Again, all that can be waved away. The porn isn't really a center point. I feel like it's there to, again, grab folks quick, but just like ole buddy said: It's a horror game with porn in it and NOT a porn game.
That being said, you could have taken that out and you won't miss the core point. That's all I'm saying. The happy events do not center around nudity like that or can just have them with lil clothes on. The happy events don't really show sex like that unless I'm missing something.
Are you one of those that don't mind the lewd scenes and skips them, or do you actually like those scenes?
For one, the game is a realistic take on the harem genre, where the protagonist goes around banging ererything. Except here the girls act like real characters, and it has very serious impact on them. This is already one of the themes that wouldn't really work without the sex scenes.
-For Ami's story it looks like the choice on wether you do her or not will have massive impact, and the game repeatedly mentions incest. Doing her actually leads to multiple horror scenes related to incest, which would also have to removed. Also, during a sex scene she calls sensei daddy. Go back to the point where you choose lust names and try daddy, you'll see it's pretty big stuff for her
-For Ayane, you would be lacking a lot of context, both on Kirin busting in on you and forcing a threesome, and the pregnancy. It's hinted the reason she shows up on the latest reset is because she carried Sensei's baby, that would have to go.
-For Makoto, the way Sensei uses her drives her to suicide.
-Haruka's entire arc, if you do her, revolves around her guilt of cheating on her husband while falling further and further into the affair.
As for the happy events not centering on nudity, uuuuuh, are we playing the same game? I think at least half of the horror scenes feature full blown nudity, and in some of them it's very relevant ( Maya on a cross and Maya in the weird sex machine are prime examples ).
At this point if he wanted to do a no nudity version, if would either be a completely butchered version that lacks the context from a lot of the sex scenes, and many of the horror scenes removed, or he would have to completely redo those scenes, write new dialogue to use another plot device instead of sex, render new scenes, etc. And this will obviously take time. Not to mention that he would have to maintain 2 different versions of the game. What I suspect would happen instead, is before any sex scene, you would receive a warning with a choice if you wanna see the scene or skip past it, with the scene still happening.
As for your last question, even if it wasn't aimed at me. I don't play the game for the sex scenes, but I do enjoy the sex scenes. Some because they are nice horny time, some because some horror shit is going down. And I very much doubt that a lot of people skip the sex scenes.