> Arguably, different responses would increase replayability.
Yes, but I don't think we're talking about the same kind of replayability. Certainly, not the kind I care about.
To me, replayability is a carefully constructed experience, by an author, and you explore it and find different things about it (say, like Adam Cadre's "9:05" [1]). But you can share your experience with another human, you can both go the same way and experience the same thing, and discuss it -- "hey, remember when you face the trolls in the cave, and...".
With an unconstrained LLM, you lose this. Plus, with no authorial voice behind it, I don't really care what a glorified stochastic automaton can produce.
(In case you're wondering, I find myself distancing from classic sandbox games as well... I used to like them, now I find them "too much work" for not enough payoff. With some exceptions, I much prefer a carefully curated gameplay experience).
I'm not suggesting to let LLMs create important parts of the game. If you want that, you can already play AI dungeon since 2019!