Lack of good storyline.

It's funny, it's tense, it features two great performances from two actors and the director expertly creates a web of odd tension where you actually don't know what is happening for the majority of the run time.

The plot isn't so bad, but the pace of storytelling is too slow which makes people bored. Certain moments are so obvious and unnecessary for the main plot. I would've fast-forwarded those moments if it was an online streaming. The ending looks like implying a sequel, not sure if this movie will get one

I think this is a new genre that they're all sort of working their way through it and haven't got all the kinks worked out yet but it's a genre that works for me.