It wasn't art fatigue that annoyed me. I don't care about seeing the same tapestry or window over and over.
What annoyed me was that after playing for ~10 hours, I started to recognize the entirety of sections (chunks) of levels that were reused. When you're in a cave, and the cave takes a turn to the right and immediately descends down to a rock bridge over a stream - just like the ten caves before it - it kills replayability. For a game that is supposed to reward exploration, designing levels in that manner seems like an odd design choice. It's probably why I played for ~40 hours and then gave up before even finishing the game.
I understand the challenges of scope and the need to find an efficient system to design the world and its levels. But they should have gone with a level randomization similar to Diablo 2. That game also reused art assets, but levels never became repetitive because, except for very specific parts, they were truly random all the time.