I'm waiting until the conclusion of the goblin arc to do a big replay of the game so things might have changed and my knowledge of the game is simply outdated, but I get where Big Green is coming from. The game still operates as a porn game meant to sexually satisfy the player first, occasionally prioritizing that over a 100% cohesive storyline. Despite the dark story and extremely imoral characters, there's little or no depiction of absolutely non-consensual sex acts without the player directly supporting it through their choices (yeah there are like over a dozen scenes where characters didn't want to do it but, even if not necessary, the villains always mindwash/mindbreak them into wanting it before the scene goes forward).
As for the NTR thing, I'm sorry but I have to agree that, at least back when I played, Alexia's plot and narrative were pretty much barebones without it. I was always confused when people referred to her as a "second protagonist" or a "deuteragonist" when a lot of her events went more or less like this: "Alexia thought about doing something, but then she realized that to go forward with it, she would have to come within the general vicinity of the Twins or some other overtly sleezy character. So instead, she chose to go back to her bedroom and sit on her thumbs for the rest of the week".
The storyline of Alexia or Rowan not cheating on each other was underdeveloped when compared to the alternative, which is understandable since porn game, but that's part of the reason why I have been wanting them to settle on some kind of open-relationship arrangement since forever so they can do more in the story without it being cheating on each other (mainly why I'm excited to check out X's and Greyhide's reworked content when I get to replay).