What I hate is when the characters get together but before they even have a proper romantic relationship it jumps to get "get mommy pregnant" or something
I don't mind background reuse as much as character reuse, because the background is just to set the scene, as long as everything else is good it's barely noticible
Sometimes, I know not everybody is able to completely edit a 3d model, but if that's the case you really need to make your story or characterisation stand out to compensate
In regular games if I'm really enjoying a game and want to keep playing after the story achievments give me something to work towards. In porn games I'm not really interested
If a game has made some effort to have unique characters, not just what ever default daz or HS2 model they can find, then it's more likely to stand out to me