Tom Stempel wrote:
"The opening twenty minutes of the film establishes the O'Brien family, although we do not get their name in the film, and we know they have children, but who and how many we do not know. The main "event" in this section is the news delivered to the family that one of their sons has died, but we have no idea which son. Putting the news of the death at this point in the film (you could recut the film and place it much later, after the main body of the family sequences) gives it an importance that the rest of the film does not support. It is like putting a tuba solo in the first movement of a symphony and then only getting a few notes from the tuba in the final movement."
I think that this is right. During the car ride home, I mentioned that if this film is about something, then it is "about" the death of a son/brother. Stempel's post articulates the reasons why I felt this way-- because the film does, to a large degree, lead us in this direction. The opening moments establish this death as a Major Event. That opening promise is never fulfilled, though, and that's at least part of the reason why I felt cold toward Tree of Life.