Finally someone put it into words, pretty much reiterating what you just wrote but I really like that control you have over the content. With a male protag it's obvious you'll want to fuck everything and that's it. There's also the fact that every girl will be similar, just a difference on body type and sex position. With a game like this in which you plenty of enemy types to choose from makes it more interesting. Will she get raped by the imposing minotaur that is sure to give her a pounding? Or will she be covered on slime?
And choosing how to play makes it more appealing,
you can sort of roleplay your main character, is she clumsy? naive? overconfident? will she get raped because of it? Or maybe she'll stay a virgin and only get her clothes ripped.
With a male protag you pretty much have to rape everything you come across. It wouldn't make sense for the rapey orc to do a no rape run.
You can have control over the content as a male protag, particularly if you have the monsters acting like monsters and not just subs. Have the monsters dom the player raping the player just as you would if it was a fem protag, just have the monsters be fairly attractive.
Every girl doesn't have to be "similar" if you put some creativity into it, and even if it was, I would prefer it to it just being the same character.
You can have monster variety, and you don't have to make everything incredibly sexy for it to work-- obviously there has to be enough to be attractive, so you probably aren't going full monster (though that might be good for a really niche beasty crowd), but as long as you make it sexy in some way, it's fine.
I know when I play games like CoC I don't want to just fuck everything because there are consequences and scenes that I don't enjoy watching/reading.
I definitely don't get the wish to roleplay a woman getting fucked unless you are gay, a girl, or maybe a cucklite.
In any case, you could absolutely still roleplay a male MC just as you could a femprotag, including doing a no-sex run (as I have attempted in CoC).
I'm not suggesting the MC be a rapey orc, quite the opposite. You are a human male that gets raped by female monsters.
After all this, the only appeal I can see is that you can have a horrible monster as well as a sexy woman with no crossover: the horrible monster doesn't have to also be sexy, since the sexy part is already being fulfilled by the protag. To me at least, this in no way makes up for the fact that it's the same eye-candy in every scene, and you have to play a femprotag, though.