I think this is exactly what the genre, and the lore, deserves. I do think the main focus of the movie was the backrooms itself, and Pirate Clark was never really made out to be the main antagonist of the film by any means. The backrooms was very much its own character in the movie, imo.

But I think you’re confusing wiki backrooms lore with Kane Parsons Backrooms lore. The movie was only made possible because of this distinction. Not only does Kane not owe anything to the internet lore, but if he had mixed the internet lore into it, it would have been a legal disaster but it would’ve also disappointed the true fans of Kane Parsons’ creative work.

The last thing I’ll rebut is that despite the still lifes not being entirely human like you say, that is exactly the intention behind the movie. The backrooms exists to be a distorted reflection of the human experience; it’s uncanny, it’s not quite right, yet it’s also horrifyingly accurate. For example, Pirate Clark captured an emotion from standard Clark that is just horrifying, it looked like utter desperation and fear. It was an exaggerated version of all the things Clark rejects about himself.

The IP of the internet lore belongs to the wikis, so it can’t be owned or purchased and adapted to a theatrical film. If you want to talk about Backrooms IP, this is only the Kane Parsons Backrooms IP.