Pretty average family drama, has one redeeming scene though

Rating: 6/10 (10 June 2018)

First off, there was an 8 year old girl in the theatre with her family when I went to see this, what are you people thinking?
Anyways,
The film had one really good scary moment, but by the end I didn't totally understand the narrative and had to keep looking up explanations to understand exactly what happened.
Still, my question is- why did the cult need to put Charlie's spirit inside of Peter? Wasn't the whole point to get Paimon a male host? Why keep Charlie? Also, why is it that none of the characters call the police during any of this?
The one scene that did really get to me was the decapitation scene - how the characters reacted to it and how the director chose to reveal it. I don't remember another time I've felt that much adrenaline rush through me when watching a movie. However, the rest of the film felt pretty slow and eventless, and at some points boring.
The first scene at the grief recovery group was pretty bad. Collette's character gives a total exposition dump of 'here's everything you need to know about my character to watch the rest of the film'. As well acted as it was, the movie felt like it came to a grinding halt for this, which was a major flaw in the writing.
I really couldn't take Alex Wolff seriously in this. He just seemed like just another douchey frat bro. A shame that most of the film hinges on his character and performance. He was fine in Patriots Day, but that might've been because I didn't realize it was him.
However, there were a few scenes where the actors did create good tension when they didn't have any dialogue, mainly the dinner scenes.
Also, at the very end when the Mom was floating up the ladder to the treehouse, I couldn't help but laugh, it was so unintentionally funny to me.