Most music documentaries aren't about music. They're about career or personality.
I've just watched "A Trip To Asia: On Tour With the Berlin Philharmonic" and it's a revelation. These are utterly accomplished players who've been hired by what is, by any measure, the best band in the world. However they accept that they're not creative musicians. They are instead, as one of them describes it, "reproducing musicians".
They talk about the need to bring all their different egos and personalities together into the tiny area in which they have to operate and the physical ecstasy when it all works. It's the nearest I've ever got to how musicians think.