Well after reading the Game Informer, Nintendolife, and Eurogamer reviews, I think I have a decent understanding of how good or bad the game is.
+ No more random battles. Poke'mon in tall grass are shown with a ! above them.
+ Most of the new Poke'mon designs are good. They are at Black/White and X/Y levels of good.
+ Many old Poke'mon finally get third forms.
+ Gym battles have all the atmosphere and excitement of a championship sports event.
+ The wild area is great.
+ You can fight higher level enemies in the wild area for quite a bit of challenge and extra XP.
+ Legendaries from past titles have been cut. No more broken OU/Uber legendaries taking up two to three spots per team.
- Mega forms have been cut.
- There's no dungeons at all. They are replaced with mini-dungeons no longer than the starter area in Red/Blue.
- Towns and buildings are incredibly linear, with little to explore.
- Dynamax raid battles are short and shallow.
- Animations are bad.
- Flavor text on NPCs is boring, bad, and poorly presented.
- There's about 70 Poke'mon cut from the list that I genuinely cared about. How the hell are Dragonite, and Scizor not in the game????