I think pulling Kaguya so early in the end was its downfall. She should have been a long movie villain that the Uzumaki family had to defeat. Imagine Naruto, Sakura, Shinachiku, and Hanami joining as a family to defeat Kaguya. Maybe even have Sasuke's family join in too. You can even have Naruto, Sakura, and Sasuke have a moment of "Stand back, kids. Let us show you that your parents are not to be trifled with."
Kaguya and Toneri should have been the big bosses with maybe the kids taking on Toneri and Team 7 taking on Kaguya. This way you can show both the parents and kids being badasses. I don't know. Pulling basically the "God of Shinobi" right at the end of the manga was such a waste of potential. Kaguya should have been the big bad in the movie with Toneri trying to revive her and Madara the big bad of the manga.
It would have been perfect. No romance drama BS with Toneri falling for Hinata out of nowhere. Actually make Toneri a REAL villain.
You could also do like side stories for the side characters like Rock Lee, Ten-Ten, and such and taken it anywhere.
So many possibilities, and infinite world he could have made, and like Toriyama, Kishimoto just blows his entire load in a single moment.
All because "He didn't know how Madara should be defeated"
I know that in the long run, at least Toriyama figured out a way to have Kid Buu defeated when he proved too powerful in a lot of ways for Goku and Vegeta. Even Super Buu was getting knocked around after Goku and Vegeta had fused into Vegito to fight him, plus he had trouble with Gohan when he attained his Mystic state, only winning when he absorbed Gohan into him.