An MMO where is truly feels like player versus environment and not another pawn versus environment. Stop having 300 people deliver the one lost ring to the same npc for days at a time. I think one way to do it is to provide a general prompt to GPT models and have them generate a few hundred similar but different quests that get assigned per player. But also keep track of these generated differences to weave a story. Make there be more npcs than players.
Creeper World. It’s technically a tower defense, but the enemy is fluid, constantly pouring out of spawn area. And the game has a pretty good story line.