I've got a West Marches style campaign going. Sort of anyways. It's open world, there are no "main quest lines" and it's a very come and play as you have time sort of schedule. You build your parties IC, you can build cities, towns, a home... anything you want really. It's a large game though... and every player action influences encounters and options as well as even loot for other players. Civilizations are starting to pop up as players build them (yes, EVERY civilization save for one is player-made) and so finally we're starting to see the quests that take place in cities rather than the wilderness. Does this interest you? I will say this; we welcome new players but a lot of stuff we do involves both mechanics that are not often used (exhaustion, variant weight, etc) as well as some homebrew crafting mechanics since 5e's crafting mechanics are a bit lackluster.