My immediate answer - Sonic fans.
I don’t really know what Sega and the Sonic Team can do anymore to make these fans happy. They’ve revisited the classic formula a few times, they tried going modern routes, they tried 2-D sprites in some entries, they try going full 3D and whatever. Nothing ever seems to be enough and that’s even when they’ve tried listening to the fanbase a few times.
Nothing seems to matter, regardless. The fans will find something to be upset about with Sonic. Anything.
Yeah but, Sonic did try to grow out of its one-trick-pony phase here and there. Its just the attempts were lacking a creative drive to make them work, so they ended up borrowing aspects of other games, even Mario games who were their key competitor at the time.
Somebody or something keeps throwing a wrench in whatever plans that there would’ve been to make Sonic interesting. It’s been over two and a half decades of trying but you have to credit that they are trying to do something with Sonic.