I felt a strong "not all cops" vibe while also having to watch as the film redeems a violent, racist cop despite never forcing him to confront those parts of his character. I also found a lot of the comedy pretty off tonally. And I'm a fan if In Bruges and Seven Psychopaths, so it's darkness wasn't the issue.
I read one review that felt the film didn't hit it's mark because none of the characters the reviewer felt the film wanted us to like were likable. Meanwhile, I feel like nothing about the movie was trying to make us like any of its characters. There were no redemptive arcs. All of the major characters were very selfish and self absorbed in their own way. You said there was no substance, but I personally felt the overarching theme was grief and how we deal with it and also our inherent need to find some sort of importance/meaning in our lives and the shyt we care about. The violent, racist cop didn't stop being a violent, racist cop. He did nothing to atone for his actions. He showed no remorse. He tries to find some meaning by following the "directions" in the suicide note, but that doesn't even work. We end the movie with him possibly on the way to murder some dude he's "sure" raped somebody, just to feel some semblance of meaning he felt he had when he had a badge and wasn't just a loser living with his mother.
The main character wants people to care about the unsolved rape/murder of her daughter and doesn't care how callous the means she goes about making that happen are. She also blames herself partially for it and awkwardly uses humor throughout the movie to deal with it and to keep up the facade of strong female she's supposed to have. You notice they never actually show her genuinely break down into tears. She borders on it then theres a joke to break the seriousness. Its purposely awkward, just like a dude dying of pancreatic cancer leaving funny suicide notes is awkward. The main character doesn't find out who raped/killed her daughter, so we end the movie with her on her way to possibly kill some dude she's told "definitely" raped somebody. It's not the justice and meaning she was looking for but its something. Rather than suffer the debilitating effects of cancer while his wife and kids watch him wither away, the chief of police (who personally hates that he was unable to solve the rape/murder of the main character) grasps at the only bit of control he has left and blows his brains out. In all honestly, the act is selfish as hell and saying it's to spare his family is a cop out. He's dying and there's nothing he can do to stop it. It's just another thing, like the unsolved rape/murder of a young girl, he couldn't do anything about. And somehow comedy is supposed to be infused into all of this
This isn't the quirky, Coen Brothers-esque vintage of creating comedy out of the absurd. Despite some heavier moments, In Bruges' comedy was much easier on the palate. Nothing is really easy in Three Billboards though. McDormand's character is completely consumed by vengeance to the point the viewer doesn't feel sympathy for her. At times when we would assume she would soften, she hardens and becomes that much more resolute about what she's doing. A seemingly good man tells her he's dying of cancer and her response is
Her own son lets her know she's hurting him by having put those billboards up and her response is
Just like the humor is uncomfortable, watching a movie where you feel little to no sympathy for a mother who lost a child is uncomfortable. The same movie manages to make us hate the idea of forgiving someone. It also tries to stitch comedy into suicide while also going down the even more taboo road of making you wonder if the person who committed suicide was a coward for doing so. If that's not enough, the one time we see the girl who was raped and murdered, she comes off like a typical shytty teenager and that's it
The movie pushes the ugliest, most dislikable aspects of themes we're used to seeing in a positive light. Grief, justice, and redemption are all supposed to be things we identify with and therefore make us relate to the characters, but instead we get characters who are unlikable because of these qualities. I fukk with movies that can make you feel uncomfortable and not feel the way you think you're supposed to. Then again my movie of the year is "mother!", so maybe I'm just a generally disturbed person