Lack of good storyline.

I was totally surprised at how great this film.You could feel your paranoia rise as the film went on and as you gradually learned the details of the real situation.

It's entirely possible that sending the audience out feeling lousy was intentional

It’s fine. It's literally the definition of a fine movie. You’ve seen it before, you know every beat and outcome before the characters even do. Only question is how much escapism you’re looking for.