Evennia supports using LLMs for your NPCs if you like :)

The use of models is fantastic even if only to provide easier ways of handling pre-written text; like taking player input and categorizing it according to sentiment or estimated topic. I'm playing with it in Evennia and dialogue and interactions with the game are somewhat night and day. Just not having to guess for keywords is a wild improvement. However, it's also expensive if you have a popular game at all -- but if player numbers are small, it's quite manageable.

Text generation is where most people's minds go but as far as players are concerned UX is more important than a million different room descriptions; you can always write rooms yourself.

When I was building them +20 years ago the hardest thing for me was finding people that could build the world. I can see where an LLM would be useful there, too. For a small team it’ll let you scale it up very fast.