I don't really buy this. I don't think the tech is quite there, although at this point it might be a matter of clever prompting more than a fundamental limitation depending on the type of game you have in mind. A strong enough DM AI could take a prompt like "I want to play a game with a similar loop to Satisfactory, set in Mordor at the beginning of the second age." And the AI could figure out from there, including devising appropriate constraints.