We can get even more ambitious than this, decouple the entire game engine from the story engine. Most of the times the same game loop can be themed with multiple stories. The game mechanics part of Skyrim could have been themed with a cyberpunk aesthetic and it will still work the same. Of course the assets will need to be generated too, but maybe in a decade or so it will be trivial.
[0] https://tvtropes.org/pmwiki/storygen.php [1] https://en.shindanmaker.com/744084
It's like Ender's game IRL
I can't be the only person working on something like this, though. So it's safe to say adding it to an MMO is being worked on by somebody somewhere, likely right now. That's probably the correct way to do it anyway, since running (e.g.) LLaMA locally on an end-user computer is not something that most people can do, and MMOs come with an expected subscription cost that can be used to fund the server-side text generation.
[0]: https://www.danieltperry.me/project/2023-something-else/