Like I said, non-standard story progression for any genre can be appreciated for its narrative, but most people get into a certain mind space when they start up a porn game. There is a certain direction and theme that gets them off and that's why they search for certain tags, especially the tropey ones like NTR or Harem.
If you are mature, you can still appreciate stories on their own merits even if it doesn't go the expected way, but that doesn't mean it would be equally fappable for them since there is a certain slant that they wanted to get off on when they started reading. It can still be engaging, interesting, fun, or satisfying as a story, but not necessarily be something they can fap to. And let's face it, NTR is about as tropey as you can get, and there are more people who came in wanting to fap to those tropes than the people who are primarily in it to see the MC win out in the end.
I'm not defending anyone throwing a fit because there are some good endings or whatever. I haven't played the Aya route, but the game already has a bunch of standard NTR variations. Having some routes with good endings is like whatever. Even Thug Hero Party had a really nicely done revenge ending, and that's like the magnum opus of the genre.