I too wish there had been a little more depth in this movie. However, when my sister saw it at the screening at the Belcourt Theatre in Nashville, along with many of Gram's close friends and colleagues, she never heard anyone voice some of the complaints registered here.
I think calling Gram "obnoxious" is too simplistic. He obviously had his obnoxious moments, but most highly creative people do. It's part of that artistic temperament you've heard tell of. However, I don't think most people could have registered the emotion they showed had Parsons merely been a gifted jerk. This is where the movie shines. The directors show some of the people who genuinely cared about Parsons as a person, and how his untimely death affected them.
I understand the attempt to show Parsons as more than the very pretty face and voice idolized so often. I think the filmmakers wanted audiences to understand Ingram Parsons as a human being, a guy who had a lot of breaks in his life, but who also had a legion of demons chasing him. I actually found myself liking this man a lot by the end of the movie. Parsons was a basically nice, decent guy who had a lot of bad wiring, not the least of which included an inborn tendency to addiction. I felt incredible pity for him.
I hope this movie spurs viewers to listen to Parsons' music and to appreciate the influence he had on popular music. If it does that, it has done its work well.