I'm just guessing but my theory is bright cartoony, colour coded characters, a simple easy to understand story with enough random background shit for autists to come up with lore and theories about, anthropomorphic animals, robots, several cartoon series, powerup transformations that make the hero turn gold with spiky hair. On the plus side it means there's a pretty active sonic romhacking community with a retarded amount of romhacks out there.
What I've always been kind of curious about is what is it about sonic that makes so many autists create weird self insert characters? Like more than any other autist heavy franchise autists seem to love inserting themselves as sonic characters. A good number of those romhacks are literally just sonic but with some autistic custom oc insert character instead. I can't even think of any other games where there's a romhacking community devoted to hacking themselves into the game.
