First of all that is the way it is. After Rabbi Nachman passed away there was no one who took the role as Rebbe. This was one of the main reasons the opponents based their baseless hatred and hisnagdus on Breslov, saying that one must have a live Rebbe, and they called Breslov - "Toyta chasidim" - "Chasidim of a dead Rebbe" - So the question why it has to be that way is valid, but that it has to be that way is certain, this is what Breslov was about in all the generations, this is why Breslovers were literally hunted down etc. etc. etc. - and the answer to the question can not be to take some half wit or even the smarted capable guy in the world as one's Rebbe - that is not Breslov - that is the antithesis of Breslov. In all the generations of Breslov there were always giants of Torah and Spirit, none of them ever did what the rabbis do today, they shirked away from any honor, power, prestige, anything, e.g. R' Shimshon Barsky a direct descendant of Rabbainu who put together לקוטי עצות and other important Breslov classics, he gave a shiur every midnight, and never ever would associate with those he was helping and teaching and guiding as their rebbe, he was simply like their older brother, he knew more he was more talented and holy so he shared the wealth. Not until recent times, maybe 40-50 years ago, did this disease take hold and begin in Breslov - Rabbainu had predicted it - it is a documented tradition that Rabbainu said explicitly that even in his matter there would arise fraudulent rabbis - "meforsamim shel sheker", and alas that is exactly what happened - forget about clowns like a**sh and convicted perverts like his rebbe who he still defends etc. - but even in the Nanach there are people that have built up their own rabbanut, where they are called rabbi or rebbe, people kiss their hands, the whole nauseating thing - all the time wearing a Nanach beanie and even singing Nanach and the Petek. This is what Rabbainu foresaw, and there is no refuge from the evil, on the contrary the bigger one is the stronger the evil will rise up with him, as was revealed by Chazal.
Hopefully it is now clear the first premise, that there is absolutely no justification for any figure head rabbis in Breslov, and that Breslov was nearly wiped out completely GF unwilling to deter from this. What remains to explain is only the why it is, and has to be like that, and how to live this way. Even still let it be clear that even though there are no rabbis in breslov - and anyone professing to be such in Breslov is obviously a hypocrite and much worse - there were and are always followers of Rabbainu who were no less in stature than the most leading Rabbis in the outside world - no less holy no less wise, and on the contrary.... - and these followers were always happy to share their blessings with everyone as equals, as explained above, so the truth is that there is no real deficiency, the only thing deficient is the falsehood of hierarchy where one person takes a higher title than the rest.
Now to the crux of the matter. There are a few factors.
One is what Rabbainu revealed in Likutay Moharan volume 2, Torah 80 that today no one is on the level of being a rabbi for the sake of Heaven. Even still, in that Torah Rabbainu seems to say that if the people insist strongly upon taking a person as their rabbi, then he can acquiesce. And this is what many of today's fraudulent rabbis claim, that they do not promote themselves whatsoever, they do not wish this at all that they should be called rabbi and have people kiss up to them etc., they are forced into this against their will..... Go figure, take one look at them, and if you believe their fantasy then you really need help - but there is much more, that was just to get started.
Rabbainu revealed in Likutay Moharan, volume 2, Torah 18, that even a true tzadik does not necessarily know how to give over Torah to others, and thus by their giving over their Torah to others they can be actual murderers, and adulterers, and thieves, and every evil perpetrator GF R"L every single second - so much so that even real murderers and the aforementioned completely pale against them - because a real murderer can only succeed in achieving his fancy once or a few times GF, but these people with their Torah are perpetrating these evils every second!!!!
The story is told of a Jew who entered a Breslov shteibel in Poland and went over to one of the chasidim and told him that he is a Jew who went of the derech and is mechallel Shabbos and now he wishes to repent - a goldmine! Which rabbi wouldn't get excited, another fish! But in the entire shteibel there was not one person who accepted to take this guy under his wing and be his guide, they all told him the same thing - we have no idea who your soul is, where your "place" is (as it says do not judge your friend until you know his place), how can we possible give you the proper guidance you need. What you need to do is start following the holy advice of Rabbainu, you need to start doing hisbodidus every day, you need to start getting up every night for chatzos etc. - because Rabbainu saw every single soul - from the time of Adam till the coming of the Messiah, and every single rectification for every single soul, and he addressed each one personally in the holy books he bequeathed.
Ultimately the main reason why there can not be any rebbe today, in my humble opinion, is because it is the very antithesis of what Rabbainu wants to achieve with us. When a person has a child, he dictates every single move and decision for that baby, and as the baby grows older he begins to make more decisions for himself, and ultimately he takes on responsibilities until he progressed to be completely independent. No one wants a twenty year old son that needs to be treated like a baby. In this same way Rabbainu wants us to grow up - to take responsibility for ourselves - he demanded that each person does hisbodidus and take responsibility for the whole world (-mischayaiv binafshoa kul hamitzius! - Likutay Moharan Torah 52, and also see Torah 5), and true life always presents huge challenges that are way above our heads - but the answer is not to run to some rabbi - but to run to HY and do hisbodidus and figure out what to do. Rabbainu himself almost never gave direct orders to people: do this or this, he gave aitzoas - advice, and often he expected and desired people to contend with what he told them. When Rabbi Nussun asked Rabbainu whether or not he should become a rav of a city, something he was very well suited for and needed to provide bread for his family, Rabbainu answered definitely, and Rabbi Nussun knowing deep in his heart that this was against everything he had learned from Rabbainu, mustered up mesiras nefesh to ask Rabbainu if this was really true - Rabbi Nussun was often embarrassed and petrified of even opening his mouth and speaking to Rabbainu, and here he challenged him asking him if he had just lied to him!!!! And Rabbainu said yes, that is the truth. And here Rabbi Nussun mamash put his life on the line, and asked Rabbainu if this is the real truth!!!! And then Rabbainu was happy and told him, if you want the real truth, stay far far away from such a thing.... Rabbainu revealed that if not for Rabbi Nussun we would not have left over from Rabbainu even one page of shaimoas (discarded holy items), and had Rabbi Nussun taken up the job as a Rabbi, he would have been left with precious little time to record a tiny fraction of what he merited, and he wouldn't have been able to go around from town to town sharing Rabbainu, and he wouldn''t have been able to build up Uman, in short the very redemption of Israel was at stake - and Rabbainu knew this, and decided that if Rabbi Nussun did not have the strength of character and conviction to stand up to him and challenge this directive of becoming a Rabbi, then the redemption simply could not be brought through him - HY is great, He will provide redemption a different way - as Abraham had to decide when HY commanded him to sacrifice the only continuation of HY's promise. And similarly Rabbainu told a great follower once that due to this followers tremendous impediments he was exempt and should not come to Rabbainu for Rosh Hashana, and the follower did not come, and then Rabbainu revealed that that was a travesty. And there are more such anecdotes. The point is that only the real true tzadik can take the role of being a rebbe and guiding people, because it is a very very tricky job, and only the real tzadik is capable of doing it, and even the real true tzadik - even Rabbainu expects from us sometimes to challenge him - and if we don't we disappoint him and miss the boat GF.
In Likutay Moharan Tora 3, Rabbainu explains the mishna of make for yourself a rabbi - meaning make yourself your own rabbi!!!! So when people challenge the Breslov tradition with this mishna, first of all we have a rabbi, and tzadikim in their passing are all the more alive, and he is our rabbi, and he is the Rebbe of all of Israel, as he revealing in Torah 111 and elsewhere, end of story. And if we must make decisions and so forth, then we must man up, take responsibility, make our own malchus (kingdom) "make yourself the rebbe" - sure we can and must consult with friends as Rabbainu revealed in Torah 34, but he must not go to some rabbi GF - for in doing so he empowers the exile and banishment of Jews from their settlements (Torah 61) - he subordinates his own true freedom and responsibility enslaving himself and thus invoking this submission and exile on all of Israel GF.
And for this reason Messiah can not come, because the people are just waiting for such a messiah - such a rabbi that will tell them: do this, do this, eat this, take this job, this operation, etc. - they want another rabbi to take away all their own responsibility and growth, to make all their decisions and be their figurehead so that they can be more confident of themselves and their dysfunctional society - where one hand washes the other - the people need someone to make all their tough decisions, and the rabbi needs the honor, money, and power, so he caters to the peoples needs.... and that is exactly what Messiah does not want. Messiah wants to bring us to even higher responsibility - Rabbainu said that when Messiah comes everyone is going to be doing hisbodidus - real hisbodidus - to take complete charge of their lives. Messiah will give us further direction - but he is not to be another rabbi like those we know of today GF!
Regarding the claim that rabbis are needed in order to explain what Rabbainu wrote – I have already explained fully that this can be done with the help of friends, and no rabbi should ever be consulted for such help. In addition, one should be honest with themselves, that there is plenty of the teachings of Rabbainu that are very very readily understood, and if there are parts that aren't that is how all of learning is for everyone, even the most gifted and learned encounter teachings that they don't understand properly, and Rabbainu already revealed (Words of Rabbi Nachman 76) that a person should not be deterred by the things he doesn't understand when he is learning, he should do his best to understand and move right along as fast as he can, Rabbainu said that when the person will finish the entire book and another, and will then go back and learn them again, he will see that he already understands much of what he had previously given up on. So a person should be strong and resolute to learn directly from the holy books of Rabbainu himself and Rabbi Nussun, who wrote with Ruach Hakodesh (Divine Inspiration) having our very souls in mind, and one should not see the books of contemporary rabbis as books of Breslov, at best maybe maybe (halivaye) they are not injurious and damaging, but they are definitely not to be considered books of Breslov..
Enough said for now.
Na Nach Nachma Nachman MeUman!