It's revenge porn against successful men and beautiful women who make the reader feel inferior. The husband, always employed and hard-working, can't satisfy his wife. She herself is a debased slut, often little more than an living onahole to be used and thrown away after being turned into a gibbering mess by the self-insert antagonist. It's sadistic and misogynistic
; it exists to validate the bitter otaku who get their rocks off to a comic book in their six mat apartment. They're not the losers, their peers and the women who love them are.>>182158524
You're not wrong, but there's only so much you can do with it. If there's no humiliation, or the antagonist cares for the protagonist, then it ceases to be NTR. What you're left with is a formulaic story that can only really get creative in the punishments and humiliation of the victims and that just gets stale after a while.