I think perhaps you misunderstand. I don't mind anything that's going on - but I do notice (some) character traits, and inconsistent behavior. MC's a bit of a two-faced insensitive wanker, especially considering he's the one preaching to Catherine about consent.
Now, ignoring that, yeah - the game is a good bit of fun, and I enjoy the hell out the various characters.
Correct me if I'm wrong here, it's been awhile since I played the first few chapters, wasn't the MC a virgin who hadn't even dated a girl before all this started? I recall the first few chapters had him as a skinny guy who was pushed around by all the women in the house. While he eventually grew a spin and went from a skinny nerdy looking guy to a buff and confident man, all of these sexual relationships are very new to him. I don't think it's unreasonable to protray a young man who's just starting to learn how relationships work to not have a good grasp of things.
Catherine's aggressiveness and the MC's attempts to manage it has been an ongoing theme throughout the game. I don't think he's being two faced here so much as not making the connection between
'I don't like when this happens to me' with
'I shouldn't do this to others'. That's not really a reach to me for a this character or for any 18yo who's getting female attention for the first time in his life. To say nothing of all the drugs Hunter has been feeding him that has his hormones flaring through the roof. Frankly I'm amazing he didn't say fuck it with Catherine and knock her up (though honestly impreg is a kink for me so I was kinda sad the dev is taking the MC knocking up the girls off the table).
Where he IS being two faces is sleeping with so many girls behind the other girls backs. That is the much greater ethical issue to me if you're going to have one. We the player know this is going to be a harem and all the girls will eventually be cool with that in the end, incest isn't a problem for anyone, and no one has and STDs. But if you take a real world view of what the MC's doing here he's effectively manipulating these girls into committing incest, betraying them by sleeping with other women they aren't aware of, and risking the health of everyone in the story by not using protection.
But as you say this is a porn game so we can ignore all that. The dev has to keep things moving along at a good pace. The games themes are focused far more on smut than romance so he dosn't really have time for the MC to properly wine and dine eight + girls.