I was going to say, NetHack doesn't feel sparse to me, but maybe I just have not played enough NetHack.

I think it's due to the fact that there is a fair bit of content, but the interface drip-feeds them very slowly, combined with the difficulty of the game itself that prevents users from finding all possible ways to interact with all content.

Nethack does procedural generation pretty well, and indeed roguelikes are a pretty good framework for it, because the game design tends to revolve around giving the player different options to solve a given problem and they're also not too afraid to have the difficulty vary a lot between runs.