I saw it and I loved it.
People may not like it because the subject is uniquely American. There is "folk" music in it, and there's newer music, but it's mostly about people and singing shared songs together.
It's about that short time right after 9/11, when the country came together, people helped people, and any dream about love and peace and all-that-shit was possible. Before "retribution" hit the fan. I felt that, too, and I'm glad I wasn't alone. I'm sorry things went the way they did, but I'll remember those few short days when people let you into a lane in traffic, paid for a stranger's groceries, and LOOKED at each other forever.
It's about communities of people coming together, and singing.