I dont think 100% of difficulty should be served as NMs, at all, I wouldnt say that, nor did I say that. However it currently is the case. You want a challenge? Do nightmares. Suggesting that they are hamster wheel content in comparison to literally any other content in this game is kind of silly though.
I also don’t understand the take that they are not meant to be challenging and that the difficulty is “artificial”. They are without question the hardest thing in the game not counting Lilith who is arguably broken by design.