I feel like Sonic Team is sacrificing their appeal to focus on demographics.
Like when I think of IPs/Brands like Super Mario or Sonic The Hedgehog I always so those games as for "Everyone", which allowed them some wiggle room when it comes to their appeal.
But nowadays when it comes to Sonic I'd assume they're just actively aiming at the child market, instead of keeping the appeal universally accessible (I know some tryhards like to front on this board, but believe it or not, people (both children and adults) sincerely like The Sonic The Hedgehog Brand.)
But you can see the manufactured child pandering in games like Colors, Lost World, and Boom (outside of the TV Show's over the head jokes).
Maybe it also comes with some people being out of touch with what Sega made Sonic about Sega finally caved into allowing outside material (comics, memes, and Saturday Morning cartoons) dictate for the fans what Sonic is. Even though in a sense, Sonic was technically a cultural phenomenon.
I'd argue at this point Sonic just stopped evolving, and just started being used like most cynical Japanese devs started doing to their brand. (Capcom comes to mind.)