It sounds like you might be interested in a West Marches-type campaign. It's a type of game where there are many players (typically a couple dozen) in the same campaign. Instead of having players chase a macguffin or BBEG all over the map, WM games have the player based in a town/city and strike out on missions which typically last no longer than 1-2 sessions. Every session happens with different players (whoever's available) and there's no requirement/pressure on players to join sessions. The storyline develops in response to player sessions and missions they accomplish. There's also more focus on downtime activities, since players are based in one place. From building a house to starting a family to organising a local cult, it's much more sandboxy and RP opportunities abound. I've been thinking of starting one, if you're interested, do let me know.