Until you realize that every country would now have a massive power-vacuum, most likely resulting in utter chaos, creating a world as bad as the one Hashirama and Madara grew up in. Then you also realize that Sasuke could have probably gotten what he wanted diplomatically...
I don't think you actually understand Sasuke's reasoning.
These ideals that Five Kage and Naruto harbor has done more harm than good. The fact that Indra has had multiple successors show that across many generations there have been people with the same ideals as Naruto, and it didn't change the world. While Naruto has his differences to them, there's no way all of those predecessors are the exact same with Naruto being the only one having one difference. There have been those that have tried what Naruto is trying and have failed. Sure, Naruto has unified the Bijuu, but I'll address that a little later. Insanity is doing the same thing over and over again and expecting a different result. Naruto's way has had its chance again and again and again, and what did it avail? Look at Madara, his way almost succeeded, what did you get? People living in eternal happiness, their own perfect little world. Sure, they were going to turn into White Zetsu, but that flaw wasn't from Madara's way, but Kaguya's. Take Kaguya out of the scenario and just leave Madara, you had eternal happiness and peace. Now, sure, it was accomplished in a nefarious way, but look at the end result. Madara came closest to peace than any of Ashura's transmigrants. This shows, maybe, just maybe, the Ashura transmigrants don't have it all figured out, they might be completely right after all. If the Indra transmigrant last time almost got peace, and Ashura transmigrant didn't, what does that say?
Their ideals have caused many problems as their ideals have been predominant through the world. Naruto's ideals are spreading and Hashirama once influenced the entire Shinobi system, and look where it's at. If these ideals aren't fixing anything, you need new ones. But the people with these ideals aren't going to let them be set aside to try something new because people are afraid of change and reluctant to accept they were wrong, it's basic human nature. They won't let it go willingly, so they have to be removed. What do you think the chances are that the Kages will have a diplomatic conversation and adopt the ideals of someone they see as a terrorist and criminal?
As for the Bijuu, they've been around for generations and generations and generations, and people have still ****ed up with them. Sure, Naruto has gotten it right, but does that mean everyone else will too? What happens if when Naruto dies, his ideals become less supported, less prevalent, what happens if they revert? If you give someone something and they continuously cause harm with it, will you say "Oh sure, we'll just leave it with him, he'll get it right someday and stop the damage"? No, you separate them. You eliminate the weapon. People in the NarutoVerse are too inept to coexist with the Bijuu, an they've proven that generation after generation after generation. Not everyone will change because Naruto says so, even in a fictional story, that doesn't happen(with good writing anyways).