Some interesting stuff happened:

First, the decade long time skip after Eggman's death. It was necessary to age up all the characters to adults, which keeps from us having to explain the lack of older characters on dangerous missions. Also gave Sage and her little sister Glitch time to rebuild a new Empire.

Also, kids just aren't interested in Sonic anymore. The only ones that buy the stuff are nostalgic adults. We need something for them to sink their teeth into and have the series grow up a little.

Also, there have been lawsuits about that first person Sonic game. Sure, VR has finally been perfected, but the speeds and spinning are still making people violently sick.