You really have to look beyond mainstream cinema to find him, because he definitely worked on tons of projects but just nothing you'd see in theaters or during prime time. Between the prequels and Ahsoka, he churned out indie films, direct-to-streaming stuff, lesser-known TV series. It's not that he disappeared, it's just that his visibility took a massive nosedive compared to the original three Star Wars movies.
The others are right to mention that his career suffered from massive backlash, and clearly that pushed him toward smaller projects. But before Ahsoka, there was still stuff out there - horror films, minor sci-fi, supporting roles in TV series. Nothing memorable for mainstream audiences, but he was working. It's mostly that without big studios backing him, it was hard to stay visible. His return with Ahsoka and Obi-Wan Kenobi is like a rebirth for him among Star Wars fans.