Idle worldbuilding idea:
Ask every GM you know to throw in some ideas for a fantasy setting. Putting them in a hat and shaking them optional.
A shared world could be an interesting experiment, even if the multiple GMs and players contributing never take a turn running it. The result is bound to be more diverse than one GM can manage. There is a risk of incompatible ideas and varying Weird Levels, so the person actually running the game would have to have final say, of course.
I’ve dropped plenty of ideas into other GMs’ games as a player, often involving my PC but not always - I suggested the basic concepts for two major alien races in Distant Stars and then played a human, which left me feeling a bit proprietary about the setting, guest GMing for it during the initial series and considering running it myself.