First off, the IMDB rating is too low. This film is better than the current 4.4 rating. I personally gave it a 6 because it is certainly not a bad film. It does not have a resolution that is satisfactory however and that is the worst part of it.
The film is actually visually appealing and the cast is talented and handles their roles well. Michael Shannon rarely goes wrong and he's good in this film if underutilized. Katharine Waterson is often very good, but I'm not sure she was the best fit for this film.
The plot is admittedly too complex in that it is searching for something the audience can hold onto but never does accomplish that, but the movie is NOT boring despite what some reviewers claim. Slow moving? Sure. But not boring.