I would recommend to ignore the 1 star reviews, there are a lot of people who will write a bad review of Mel Gibson no matter what he does.
To me, it was a movie which capture attention since the first interactions with the main character, portrayed by Gibson, who makes a very believable unlikeable radio host jerk, the movie plots gets you interested all the way till the end, and there some unexpected twists which make you question a few things on how much people are willing to do just to get likes and exposure..
In my opinion is a movie which invites to some reflection, if anything the end could have been a bit stronger, the acting of Mel Gibson is convincing, the rest of the cast helps on the delivery, and is a great movie with zero especial effects, which is so refreshing these days.
You need to watch it with open mind, if you are a Gibson hater, then save your time, and write a bad review, at least for me, it was entertaining, interesting and got me hooked for as long as the movie lasted.