The dungeons themselves are very boring and repetitive. There are a couple unique enemies I think.
The real problem is there are some amazing unique bosses in there. You also have to finish it to get all the achievements. There is an extremely difficult dungeon that halves your health too.
I would definitely skip your first time through. They also don’t adjust for NG+ so you could beat the game and blast through them. (Need to find some chalices again in the world I think.)
Overall they are one of the big missteps of the game.