SaraLuna
I know what you're talking about.
At the same time, if you were to see a movie that you thought was going to be good, but you were really disappointed in it, there's no reason why, to "cleanse your palate," as it were, you wouldn't want to write about that. Not as a hatchet piece, or even as a review to warn people to stay away, but just to say, "This wasn't worth it, for me, here's why, and I'd like those two hours back, please."