I think of porn games as satire. They are all mockeries or reductions of whatever genres they contain. And that's fine! That's their purpose, to take a genre or theme and make it revolve around sex.
This game is a satire of a porn game. It takes all the tropes of porn, dials them up to 100, and then puts them all in the same game. It's ridiculous, and I don't think it works well here. There's a distinction between games that have comedy, and games that are pretty much nothing but comedy, with this one falling into the latter category.
You can have too much of a good thing. Without other balancing elements, hyper-fixating on one theme can dull it. That's what happens with the humor here. There's no emotional depth, no sincerity, no tension to counterbalance the funny bits, which really saps them of their effectiveness. Likewise with the sex scenes, I'm aware that this isn't supposed to be a slow burn or anything like that, but that doesn't mean you have to go "WAM BAM they fuck, now onto the next girl."
I'm not sure if the "story" here could be told in a better way. Even as far as porn games go, "you have 23 sisters that you need to impregnate to get your inheritance of BILLIONS of dollars" is pretty out there. My first instinct would be to suggest adding some mystery or build-up, but I'm not a writer, and I'm specifically not the writer of this game. I don't know what the dev has planned in their head, and maybe the finished product will be something rather different than what we have now.