The documentary isn't about loneliness per se, and it's also not about whatever Ben Franklin meant in the original Join or Die. It basically is a biography of Bob Putnam from when he was a kid growing up in the U.S. "I think as a psychologist, absolutely, my head goes to like, oh, God, that sounds lonely"
How do friendships change as we get older? Should you join a bowling league? And is Angela more important to Mike than Mike is to Angela?