That's crazy to me. I start to get annoyed when my save game slots get to be more than 1 page.
As for tropes in incest games, I don't care as you can only write a story so many different ways. You would have to do something radical to be different to the point it doesnt make sense:
Why not have an incest game where the MC is a shape-shifting goblinlord from Circulon VI who only exists in the minds of the woman in the household who are actual homeless, corrupting the minds making them do sexy stuff with each other? Then someone comes along Screams NTR and then everyone who isn't on cuckzone hates you. "This isn't how an incest games is supposed to be, you need to have this repeated trope to be a good game"
Feel like there's a wide enough gulf (and plenty of options to fill it) between what the OP describes and what you've got here. Even small variations on what OP brought up could inject some life into things:
1) MC can be an average or ugly dude with an average or small dick that manages to seduce because of his charm or wit or because he steps up and saves the family farm or what-the-fuck-ever.
2) The father can still be part of the picture but is largely absent, work/friends/(insert reason here) keeping him away from the family and unaware of all the fucking.
3) Swap their personalities (bitchy/overbearing mom, doting/caring sister, bratty sister), or give them more fleshed out personalities.
4) Either slow burn all the relationships or make one the "main" relationship with constant sex and slow burn the rest. Or make MC someone that's always bringing home chicks and his family hears all the super hot fucking and just can't control themselves anymore. Also: address the taboo more often.
5) Limit the # of relationships/love interests or make it clear that some hookups are one-offs.
6) Add simple flaws to women, even just perceived flaws. Broad shoulders, stretch marks, dimples, scars. This I imagine is more of a restriction of whatever engine/rendering software is used so, even if I agree with OP, I can understand why it's not more common.
And so on.