And let's expand on @Sonic5993's second point: It gets worse each time. A common criticism of the classic trilogy before Sonic Adventure was even a thing was that they weren't innovative enough. I mean, consider that in about the same length of time we've had since Sonic Mania, SEGA released five mainline Sonic games (1, 2, CD, 3, & Knuckles) with identical core gameplay. Critics often compared this to how much less frequent, but how much more SPECIAL Mario's games were, and it did seem to hamper Sonic's reputation in the short term. However, the four years between &K and Adventure was more than enough time for people to miss Sonic, and running a GOOD THING into the ground matters a whole lot less in the long run, especially if you're refining the formula while you do it. The problem with the 2000s and the 2010s alike isn't JUST that the defining elements of each decade got overplayed, it's that the execution of those elements got WORSE over time. Compared to what we got, I'd love to live in a world where Lost World and Forces were exactly as good as Generations.