This is not the first time that I’ve seen the book casually criticized, and while I’m not actually upset or anything I’m also not exactly sure what was supposed to be the problem with it. You sort of have to assume a certain quirkiness from translations and Foucault’s Pendulum is probably one of the better correctives to conspiracy thinking anyway. Watching one of the characters… well, no spoilers.
PS: If you’re wondering why nobody ever made a movie out of it, it’s because after The Name of the Rose Eco didn’t want his books turned into films. Which is kind of odd, because that was actually a pretty good adaptation.