I'm asking myself this right now.
Like me just get your opinion on this: Can ideals/ideologies change? Because your insinuating that they can't, that everything reverts back after the main actor is gone.
Take any main civil rights activist and let them die (like they did) and would everything revert back?
Ideals/ideologies can change. But you assuming that everybody would follow one ideal (Naruto's idea). Watch Code geass. Before lelouch made the whole world go against him, He was able to get several Ideals/ideologies who hate each other to live and work with each other to pursuit one goal. The key was use force and show people proofs that their government is tricking them. So they only got together to overcome a problem. After lelouch made the whole world go against him and die, a lot of the major problems die with him. But there was still minor problems but not enough to cause a war.
This ninja war is over, there is no reason to go out of your way to cooperate now. It temporary peace at the moment until someone's desire get greedy. Then a war gonna birth out of place. Naruto won't be able TNJ people out of it unless he gonna take the blame for whatever the problem is.
In real life, everything don't revert back to what it was before the civil rights activist took his/her stand. But there is and will always be some problems exist in the world after the the leader gone. Someone will pick up the cape and carry on.
In Naruto's world, there is no one gonna be as strong as naruto to do so and in order for a person to be as strong as naruto, that person would need to a reason to do so or go through bad experience like naruto did. But how would that person go through those type of experience if there is peace in the world that naruto will create.