I think it's just the fact that its text based (with generally quite lengthy chunks of text between choices or actions on your part) opposed to visual that leads to this illusion. Smut is clearly the basis here, the clear focus. If that weren't true, the primary antagonist wouldn't be a psychopath trying to fuck you and the rest of the world into submission for really no other reason than that's what demons are supposedly like. She's about as complex as a marvel movie villain. You wouldn't be able to solve pretty much (or just conclude) every situation with sex, and there wouldn't be numerous entire species that are completely dominated by sex.
This game is often verbose, but it's not especially deep (or consistent for that matter). That's not intended as a criticism, just an observation. It really doesn't need to be deep (or consistent) to scratch that itch or appeal to the fetishes of its base. If analysis and head canon is your fetish, you do you, just don't expect that the writers put as much thought into each individual concept as you did.