"The Backrooms" as a concept are basically antithetical to the design style and typical experience of an HHN haunt attraction, for all the reasons Brian has already said. Isolation, the endlessly looping and ever-changing nature of the architecture, the fear of an unknown and mostly unseen creature potentially being around any wall.
"Backrooms", the 2026 movie, would be tricky to adapt, but I don't think it is totally impossible. It would lose a lot of the initial eerie concept / vibes, and likely have to fit into the more traditional HHN "book report"-y tropes and structure.
I think IP like A Quiet Place, with its' wildly large monsters and reliance on silence; or Black Phone, taking place almost entirely in a singular dark room, are decent comparisons. I didn't think AQP would ever happen for a number of reasons, but I was wrong and they did it anyways. I still wasn't huge on the AQP house in execution, because the limitations I was worried about were genuine issues with the house (overuse of stiff monster puppets, a sound "mechanic" with no bite). But I conversely thought the Black Phone house was deeply clever in how it portrayed the claustrophobic themes and aesthetics of the film.
I don't personally believe the idea would make for a very good house, and similar to AQP / Black Phone, it would take a lot of bending and work-arounds to portray in the format. But, I've seen weirder and far more niche IP included at the event over the years. The Backrooms film was reasonably successful, and it does have a very specific look and vibe to it.
Outside of really specific cases like Obsession, Hereditary, and a few others, I'm mostly done counting IP totally out of the HHN picture. I am not personally looking for it to happen, but if the HHN team wants it, they'll be able to find some way. For better, or for worse haha.