Blaze the Cat
In Summer 2016, Blaze the Cat had met new friends that were specifically designed to be in an independent franchise made just for her. Subsequently, Blaze decided to leave the Sonic franchise after the Rio De Janeiro 2016 Olympic Games to start her own. (This also explains why she wasn't in "Sonic Forces", and why she objected to being put in post-2016 Sonic games such as "Team Sonic Racing".)
Before leaving, she told her voice actress at the time, Laura Bailey, that she was seceding from the Sonic franchise after Rio 2016, and Laura Bailey went along with it and moved on to something else.
Either that, or the timing of both departures was just a coincidence.