I really wasn't a fan of the movie. The actual Backrooms were neat to see, but the plot was very meh.

Then again, I very much prefer the Backrooms stuff without all the, for lack of a better word, "plot" around it - monsters, human organizations, etc, etc. What's far more unsettling to me is the idea that the entirety of the Backrooms is devoid of life, and there's no "reason" for it to be there.