1) A different perspective might help. Viewed from a different way, Harry Potter isn't the hero so much as the rallying point. Everyone else does significantly more to effect Voldemort's demise (except at the very end, perhaps). Harry isn't a hero, he just happened to survive. That shows that it's possible, and people are a lot more willing to try with a little hope.
2) People clearly have no idea how to handle dark magic. This has always bothered me about magic settings in general, but it's particularly true here. There's some class of super awesome wizards whose job is supposedly ferreting out dark wizards, but they don't get much air time. I think this is the source of the Voldemort frenzy. He breaks the rules and no one knows how to stop it.
3) For all that they are powerful magicians, the majority of the cast is either a student or a teacher. There's like two people who actually know what they're doing (Snape and maybe Sirius).
I generally agree, though. I think there's one movie I actually liked most of, and then only parts of it. The most interesting character by far is Luna. Most of it is too trite and way too prophecy/destiny driven for my taste.