It happens from time to time.
You begin watching a movie and its purpose seems clear, and everything that might come of it promises to be entertaining. Or maybe the actors share great chemistry, and you want to know which direction it will take.
But then it slows down, or the characters behave in a way no real person would, or the director has grossly miscalculated the appeal of them, or how noble its final goal really is.
And then it occurs, usually around the one hour mark, or 45 minutes if one is really unlucky.
The movie slowly descends into mediocrity, a change so gradual that you did not even realize. By the time you do, you kick yourself in the head for wasting 90 minutes of your life on movies so, so, so terrible.