Depends on the players and DM as to what they expect I believe. Some folks do want to suss out what the red dragon must eat all holed up in his cave or dungeon. Some not so much.
Gary may have talked ecology in the DMG, but when he wanted to add something crazy to his famed castle, he just say "here's a demi-plane" or whatever. (Though I think, with early TSR at least, poor editing and proof-reading probably had more to do with the wacky dungeon dimensions and mismatched monsters than anything else.)
Some folks want to do demesne level of play, and others want to spend time in the dungeon. I think that there are a lot more role players out there in the wild world nowadays than roll players. My oldest DMed her siblings and I and our friends in a 5e game and she was asking us to be descriptive in describing the death blow - something I just do as a DM in my 1e games. Both ways are fun for all.
Super interesting topic though!!