Im gonna say something and I kinda hate myself for saying this. It may have been my mood, but I felt really strange playing sonic 3 and knuckles recently, not in a good way. It had been a long time since ive played it so. Like maybe 4 years ago since ive last finished it? In my mind the sonic 3 part of sonic 3 & knuckles had never really been the good part so its actually not that surprising, but I dont remember finding it a chore. I think sonic 3 alone is not as good as sonic 1 & 2. Maybe i'll enjoy myself more when I play from mushroom hill zone. Yeah I think flying battery, sandopolis, lava reef, hidden palace, sky sanctuary and death egg are definitly a lot better zones than what sonic 3 offered.
My issue with it is kind of the same with what I have with most modern sonic games, which is lack of interactivity and more of a showcase of how cool it looks when sonic speeds through, kinda like TA here above me mentioned. Even the final zone, launch base zone, which you'd expect to be more serious and challenging lacks any of that and you just kind of speed through it till the final boss.
My hope is that sonic mania adresses this in a way. I mean at the end of the day there's more to sonic than just an engaging videogame. Sonic games and their playfulness with the physics is something that doesnt get old. But it would be a huge improvement from s3&k