Yeah, I agree about the fact that it is kind of shallow especially Kevin. I hope the devs are still active tho. Other than Thomas' route, they are kinda feeling incomplete.
Anyway, I have several nsfw games in mind: COOT (as you mentioned, Ian is still a king in my heart), Straight!? (Only focus on one love interest, but the character development is a chef kiss), Dead Dating (Still in development, but it's been great by far, the art is just gorgeous.), UncleNeighbor (lots of daddies, but the downside is that the story is not constant. Like there are routes to choose for individual characters, but the routes will not affect each other), From the top (Also in development, bonding takes time, and it feels like real life, not in a porn game. Downside would be that everyone has a hairless body).
Oh I almost forgot, is Norman's route always ends the same that he'll rather date a girl instead of us? Just asking. but if you happen to know the other ending please tell me lol. I'm here for Norman 24/7