She actually starred in Mother! Which is probably more disturbing than Saya for most people and it still got a bunch of awards
No it didn't. It also barely broke even and was an incredibly polarizing movie (for some reason, considering it was trash). The only award of any actual note or merit it was even considered for was the Golden Raspberries.
This isn't anywhere near the first movie where sexual themes are explored with a non-human entity. It was pulled off with Under The Skin, Teeth, Splice, and it's predecessor 'Species' and pretty much any 'weird science' type movie with a higher than 12 rating. These movies get made.
Under the Skin and Species present the non-human entity as the antagonists, Teeth is a comedy where basically non-consensual sex is the trigger for castration via vagina. These are different things outside of the vague similarity of 'horror' or 'science fiction' with 'naked girl'.
Saya no Uta isn't trying to make some broader point like Under the Skin does - where the sexual aspect is purposely downplayed - it's literally a game about a childish Shoggoth cannibal and the irredeemable fuck that enables her. He is rewarded by his deeds and for the entire climax of the story - and thus a film adaptation - it would have to literally sell the relationship in a way that a film would likely not accomplish nearly as well as it should. And this is without going into the logistics of making the meat world play well on screen.
Women being eaten by monsters is about as old as cinema itself so I don't even know why you're pretending that is an issue.
Because movies don't tend to actually show human people eating severed limbs. When monsters eat people in movies it's either bloodless (see: Jurassic World), it cuts to black, or it cuts away as the human is dropped into the mouth. Other times it's shit where something familiar, like a shark, eats someone and all there is is the blood on the water. That's quite a bit different than having two people casually eat a person over the dinner table and using the jelly shit is even sillier to imagine on camera as it was in the confines of the story.
Just because movies have done something doesn't mean it's done well.
Being turned into a fuckslave would be controversial but could be fairly tame if the shift it more to a 'timid servant' and play up the fact that she had a crush/ was already attracted to the main character so the sex isn't non-con just being turned into a Cthulhu is the main source of anguish.
There is no scenario in which a poorly written character like whatshername who exists in the plot solely to become fuckslave is done well - especially not in the current climate around Hollywood. Even if you take away the fuckslave part and make her mindless maid on a collar or whatever, that's not a character or role that will go over well and is better stripped from the script altogether.
You seem to forget there were 3 supporting female characters in Saya No Uta. The Doctor was essentially the anti-hero adversary. Hollywood continues to get away with far far far worse in regards to female representation so I can't see this being a problem.
I barely consider the friends to be characters. They're basically the first victims in a slasher movie. The supporting cast as a whole was pretty under-developed since that's not what people came for. Hollywood is far, far, far from perfect or ideal when it comes to great roles for actresses, but any adaptation of this work would need massive re-writes or else they just cast unknowns on the cheap but then you lose out on people who see movies based on name recognition.
'Feeds on Semen' is a unnecessary eroge detail to amp up the blowjob scenes. The analogy is clear, she is a black widow spider/brood mother/plague. They could easily change it to 'his sexual energy' or 'his life force' and nothing is really going to be lost in adaptation in terms of plot.
Yeah and then people are laughing in the theater as characters talk about 'sexual energy' as if they're watching a shitty hentai.
Once you remove the unnecessary shit Saya isn't as hard to adapt as your trying to make it out to be.
It's not as simple as you're trying to make it seem. It would require major rewrites for market appeal but the appeal is already super low. It would work better as an independent film where they can get away with more but then they'd have to have good fucking luck at getting it screened in major theaters. Just because something works in one medium doesn't mean it'll make the transition to another smoothly.
In other news, Aquaman was a garbage movie.