Even outside the fact that a lot of it are simple fetch quests, I feel like the the vast majority of quests involve interacting with NOTHING but broken machines and it makes the entire zone a bit of a chore. I feel that thanks to the lack of real NPCs there’s no plot, no real motivation to do stuff and not even any flavor text or anything else that might distract from the mundane nature of your tasks, something that is especially bad because the hook of a mine being full of demons that have broken loose sounded cool… yet you then find out that the only thing they did was mess with a lot of plumbing and you have to fix it.
I think that putting in some real NPCs would help a lot with things. Make them some of the miners that made their way out or managed to hole in before monsters swarmed the place. Maybe mercenaries that were brought in to help with the huge number of monsters and struggle to even get things done while they defend themselves. Invent a magical radio that allows you to have discussions with people on the surface and add more flavor text beyond “This pipe is broken. Better go fix it!” ANYTHING would help to make a sincerely kind of drab area feel more bearable.