Yes, the book had some problems, but Rowling's greatest strength has always been describing a given age group as it actually is, and well, 15-year-old boys are like that. Sirius, to me, represented the dangers of _not_ growing up, and Dumbledore of the overprotective parent who wanted to keep Harry young and childish. The point of the book is that Harry has to grow up, whether or not he wants to, and accept responsibility and consequences. That's why the scenes in Snape's Pensieve are so key - Snape has never really let go of his adolescence or his adolescent hatreds, and neither had Sirius. Remus, otoh, has.
That, and Hermione is Always Right. Which does get a bit annoying.
That, and Hermione is Always Right. Which does get a bit annoying.