I think the critics misunderstood the film. The message of the file is how living with a lie can eat you alive, and it’s sometimes very difficult to truly know someone even if you think you know them.
Mental Heath is complicated and the movie does a great job at taking the audience through some of the various feelings including: pain, numbness, loneliness, helplessness, fear, etc. Sure, many of the characters are more like caricatures, but they help to show the different ways people deal with grief, and other life stresses.