"Why the ambiguos/generic dungeons of Oblivion are in retrospect a good thing"
I realised this a few days ago whilst exploring an Ayleid ruin. It was a ruin I'd probably explored before, but could not remember/identify it, because like all dungeons in Oblivion, it was pretty non-distinct. Now why is this a good thing? Well, that I can forget a dungeon, and explore it a few years later and feel like it's new, extends the life of this game even more. Wheras the dungeon's in Skyrim, with their hand-placed storylines and mini-plots are really a one-time affair, like knowing that the Redguard family were slaughtered in the lighthouse to the north, really negates any reason to explore it again in subsequent playthroughs.
Oblivions dungeons force me to imagine my own scenarios and reasons as to why I'm there.