There's a lot of really cool things in the 2024 books. I'm going to use this space to talk about what I've liked.
First and foremost, this may seem shallow, but the art is phenomenal and that matters a lot. For what feels like the first time to me, D&D art isn't just self-referential, it is fresh. There are legitimately cool ideas for what characters are and look like, and new aesthetics to explore Fantasy as a genre through. More then ever does D&D feel like it aesthetically stands on its own two feet to me in the contemporary/WotC era.
Next, the classes are just flat out more fun to play and more fun to DM for. There are some sensible new limitations, like Paladin's not dropping two mega smites a turn or Druids having a menagerie of wild shapes instead of an infinity. But there's a lot a lot of cool things mechanically like weapon mastery that make for more exciting combats. Finally, combat in D&D feels more dynamic to me, because using weapons leads to interesting changes in the environment and the game state beyond just damage being dealt. "Push" and "Trip" are, frankly, revolutionary despite being minor and simple, just because they make use of the entire space instead of isolating things to 5 foot squares. Other classes, like Sorcerer, have more of an identity now, and classes like the Barbarian no longer feel like the same old trick at low and high levels alike. In other words, the game has more texture now, and that is display primarily through the classes.
The DMG is a far better book now. It provides good advice that IMO is a great refresher for experienced DMs. It has good tables and solid ideas for running the game and changing it to suit your needs. It fixes issues with the Adventuring Day, it gives an actual exploration procedure, and the Greyhawk redux is a great foundation to use for one-shots and quick games. I like the various bits of advice for worldbuilding in here too, and will be using some of them to make my own personal "Material Plane" for funsies shortly -- things like creating one god per plane in the Great Wheel to make your own pantheon, etc etc.
Overall, the books create a better foundation than 2014, and are IMO a flatout upgrade as a GAME. Highly recommend.