I disagree with the majority. I like this MC.
One of the features of this game is that the MC is not a "seducer" or a hunter.
He is, one might say, the prey and victim of someone's plan.
At the head of the story is that Becca actually makes him look at his daughters from a different angle and accept hidden feelings.
Unlike many other games, MC is primarily a good person and a father. For him, this is new and dreadful.
And I like his constant struggle between his desire and what is right. This sets this story apart from other similar games.
To be honest, if the author removes MC's uncertainty, I will most likely lose interest in the game, because it will turn into another banal sex marathon with a perverted father.
I don't think the issue is so much his normal character, it's the to the level of uncertainty that the MC keeps having because no matter your decisions as the player, your character does not progress. In VN terms this is emotionally. It is too soon I know, but some indication of progress would be nice. There are also some inconsistencies that I'll get into in a moment.
I was frustrated with the scene as well, but for different reasons. Why the fuck does anything going on be conferred as Taboo by the author? They are not related, nor are they under 18 (legal binding age) much less the age of consent. But these two hangups seem to be his largest ones. Why?
He's always going on about how he's so screwed if anyone finds out but the worse that would happen is he looks like a prick for running away with the ex's daughter(s) or breaking the half plus 7 rule. The MC should not be obsessed by this. His Ex may use it to fuck up his life in some way, sure, but that isn't a taboo problem.
Also, we have two MCs occupying the same body. One is an adult male, the other the father.
The adult male watches porn, fucks a lesbian and dreams of his daughters having sex with each other.
The father has never heard a woman call herself a whore in bed, would never even think of touching his daughter and refuses to acknowledge their feelings.
The Author seems to switch between the two as needed in the story vs a good merge. I expect writing issues from amateur writing so it's not so much a big deal as pointing it out. The MC based on written should know the difference between a girl calling a guy daddy in bed and wanting to fuck their real dad just on the fact he watches porn alone much less fucked more than one girl. He even eludes to it in an internal dialogue. So why does he have Becca explain it again?
If anyone in the room has mental issues, it's the MC. He's so convinced he's the girls real dad that doing anything with them is incest.
And maybe this was Becca's real reasoning for the big plan. She knew all the girls real feelings and knew that the MC could never JUST be their father. He had to be more than that for them and set about her plans.