You do realize that IT is a masked final, FINAL end. You don't? It's alright I'll explain in detail.
IT is basically a Genjutso that traps the minds of people into a different world, some sort of a shared hallucination, where people regardless of their life stats would "live" together in peace, single minded and harmony. So far so good right?
Seems a rather harmless desire to force people to live in peace and harmony even if they don't want to, no?
Yet, as always in these great plans, there is a but. And in this case a huge, massive and critical but. People who are targeted by Tsukiyomi don't move. The Genjutso blocks and locks the mind inside itself and cuts all ties with the body, hence why it's so difficult to interrupt it unless you are a Jinshuriki or (apparently* a blood relative).
Ultimately this "but" is what makes IT definitive and unchangeably fatal to all who fall under it. IT is nothing more than the prorogation of Tsukiyomi ab infinitum, which means that instead of lasting only a couple of seconds like Itachi's did. IT would last undeterminably through out time, minutes, hours, days, weeks... I could go on but after two weeks the human body shuts down due to dehydration, which could be translated to massive collective death of the entire human race.
So in sum, if the IT is successfully launched the story ends, period. And it ends badly!