Bernstein really was as brilliant as his reputation suggested. Every note of every phrase had a meaning within the context of what the composer might have presented had he/she been on the podium to conduct. Bernstein didn't just conduct music. Music could actually come to life by way of Bernstein's baton.
Maestro explored things about Bernstein that we'd heard about and maybe peripherally realized, notably his sexuality but also just how consequential his wife was to him both personally and professionally. Was she the rock to whom Bernstein could find refuge (though not necessarily without some reservation, as the film pointed out)?
The film laid bare some of Bernstein's personality and motivation, though exactly how these facits fit together was not really explained though that may have been the point: we can't do it.
Closing the film with Mahler's Resurrection Symphony was an excellent choice. It is an incredibly complicated piece of music but when performed properly, is a powerful unitary force. Bernstein was one of his generation's greatest interpreters of Mahler so those performances were transcendently wonderful.
Maybe that is the point: Bernstein was a complicated man who could somehow bring it all together through his music. Bernstein could deliver -- on the podium -- a unity of purpose which seemed to be diverse and conflicted and far too difficult to experience in his real life.