i think the big one is that there is no broad scope or scale to the films, no sense of mystery or mythology, etc.
they're very safe plots, very sterile, but instead of building a universe or expanding the scope, creating things to imagine about etc the new star wars movies just regurgitate the original plot points and use assets from the original star wars movies to set up very simple plot points.
for all the shit that people give the prequel trilogy, and most of it is rightly deserved, they had this massive universe set up, and there was an ambitious scope. you had a real galaxy with planets like Naboo and Geonosis, actual wars like the Clone Wars and battle for Naboo, the Jedi/Sith Order is expanded on but still left mysterious, there's new concepts like pod racing thrown in there, etc. there's even a political subplot.
You never feel like you have a grasp on everything that's in the Star Wars universe because there's never a finite amount of things in that universe, and that's what makes the movies so fun. everyone who watches even the OT feels like Luke in A New Hope, where he's looking at the stars and all the possibility of the universe out there. i think that is what makes Star Wars such a good franchise, you can imagine so much more.
Meanwhile the new movies are just typical character action movies with a lot of Disney staples in it and all of the "Star Wars" aspects just feel like they shifted in a few assets to remind you what franchise this falls under. What makes a Star Wars movie a Star Wars movie? Is it because it has X-Wings and Lightsabers or is it because or the universe, the wars, the fusion of fantasy and sci-fi, etc?