The idea of Otsutsuki was actually good but Kishi executed it badly because he was doing everything in a rush instead of deciding to take a small hiatus like Hunter x Hunter's authorThe story was about Naruto. And I think Kishi should have focus more on the "griminess" of the ninja world than giving us bullshit. Kishi became more mainstream after Part 1.
I dont see why people cant change their goals. Sasuke path was never a solid one he was always dealing with the trauma of losing his clanif story focused on sasuke's POV then it would be the most unstable manga ever existed. The guy couldn't stick to a single goal.
He wanted to avenge his clan but he took a turn and decided to destroy konoha. After getting Itachi's eyes, he decided to protect konoha and tried to become hokage. Like wtf? It sounds like some crazy psychopath.