They made those shitty extra characters and the chao garden mandatory. Tails is now a robot cause we've had so much fun with the robot the first time around, and his missions are accompanied by constant beeping. Knuckles' emerald scanner now can only detect the emeralds in the order that the game dictates it, meaning you could be running around one of the emeralds and never see it because you first gotta find the other one. Sonic can no longer spin-dash while running, gotta stop in tracks. The light dash now only works when there are rings around, so that you have even less freedom of movement. Boss battles are still as braindead. There are no hub areas anymore. Enemies sometimes spawn right before you as you're running. Levels are much poorer designed. The sensitivity on steering while running at high speed is insane. I could go on really, they've just ruined everything that made the first game fun.

And the presentation is somehow much worse too. I dunno why they sucked all the color out of it. The first game was so vibrant, and this one is just bland. Some weird musical choices too. Knuckles now has rap songs, apparently written by him, since they speak about him in first person.

While this is clearly worse than the first game, I think I could've played through the Sonic levels and it still would've been a decent game. But because they're now sandwiched between Robot-Tails and Knuckles levels, I can't. It is torture to play those two.