I've been reading some reviews of 'Room 237', both before and after watching the film itself, and it seems to me that the people who liked it all had one thing in common, and the people who disliked it all had an entirely different thing in common. To wit: People who hated the movie thought that it was about 'The Shining', and people who loved the movie (and I confess, I count myself among their number) thought that it was all about the interviewees.
And in that light, I think that both sets of reviews make perfect sense. Because as a movie about 'The Shining', 'Room 237' clearly fails. The interviewees are all (in the immortal words of XKCD) raising confirmation bias to an art form, viewing the film through the lens of their own preoccupations and focusing on irrelevant (or in some cases imaginary) details in the mistaken belief that Kubrick's "perfectionist" tendencies and refusal to provide people with easily-digested homilies about what his film "really means" translate into coded messages hidden in the film for the diligent. There's no benefit to be gained in listening to these people talk about how this is really a film about the Holocaust or the genocide of the Native Americans or the secret conspiracy to fake the moon landing footage, or at least not enough to justify sitting through a documentary on the subject.
But if you assume instead that this is a movie about obsession and fanaticism, about how a movie can become a sort of cinematic Rorschach test reflecting our own thoughts and ideas back at us, then it becomes fascinating. By allowing each of the interviewees to speak, unfiltered and uncensored, the film becomes a sort of Freudian analysis of the kind of person who would fall down the rabbit hole of conspiracy thought. Hearing person after person offer a variation of, "I don't know why nobody but me sees that this is what Kubrick was trying to do, maybe it was because I was thinking about this so much just before I saw the film..." It's illuminating, as well as tremendously entertaining. (At one point, the camera freeze-frames on a scene where one commenter claims that Kubrick airbrushed his face into the clouds...and just pauses, as if to say, "Yeah, folks. We got nothing.")
So when you watch 'Room 237', don't think of it as a movie about a movie. Think of it as a movie about the people who watch movies. You'll be much happier.