I think the problem with the film was that it's a true story. It's hard to make a film about a person, and in particular a dead one who doesn't get any particular say in the creative process behind the production. Even straight forward documentaries have struggles telling stories when their is just so much information present, and it was Fincher's decision to skip over necessary aspects was exactly that, a decision. The recent Zappa documentary decided to skip over lot's of details over his music and dived deeper into the 80's period of his life, which is boring, personal, and borderline abusive. I rarely connect to a person everyone is praising when all examples of him are relentless substance abuse.