I tend to agree. I used to run Call of Cthulhu in high school, and there was a lot of preparation involved in running a good scenario. Some people are good at winging it and making stuff up as they go along. I never was. The best experiences for me and my players was always when I'd meticulously designed my own scenario, or used a store-bought scenario and read it thoroughly. Either way, hours of prep.

I would love to have an AI as an assistant Dungeon Master (or game master, or Keeper, or what have you). That is, one person in a group of players maintains the role of a master storyteller, but the AI is ready to fill in details or suggest ways to get the players back on track. This would probably be tedious if you're interacting with the LLM entirely through text, and having to manually keep it up to date with the story. But it could work well if you have a model that understands spoken language listening in on the game and generating cool images and making private suggestions to the game master.