I know it's hard to accept for a lot of fans because you always wonder who is responsible for some of the horrid changes but the person to blame isn't really Kloves. Kloves really does have good intentions and the script is safer in his hands than anyone else's because he has such a strong connection with Jo. Even though there are times I get angry with him and his changes, you have to remember not everything he writes gets translated onscreen
properly. That's the key word. I remember how upset and angry I was when HBP came out; I was frustrated that Ginny's character was so bland and boring, nothing like her fiery self in the books. I blamed Kloves all the way. However, when WB released the script for the Oscars last year, I was shocked to see how Kloves had written the lines, and how badly they'd been translated on screen by the actors/directors. When I was simply reading the script, I heard the voices of the characters from the book, presenting their lines like their canon-selves would. When I imagined the actors, however, the same lines lost their edge because the actors didn't perform them like the characters.
When OotP came out, it was horribly done (and the worst HP movie to date in my opinion) because Kloves wasn't doing the writing. Michael Goldenberg wrote the screenplay and we all saw the consequences of that. He did a good job I suppose but he didn't have that relationship with Jo, which is where I believe the film went wrong. I think if there's anyone to blame for the crappy translation of the story, it's Yates overall. That's the pattern that I've found with the films. Since he's been directing, the films have gone downhill in my opinion. His directing as been improving for each film, (HBP was loads better than OotP because Kloves was back again) but it's nothing compared to the first four films. Before we all jump on Kloves, we should really think of what a hard job he has. He has this huge fanbase to please, yet at the same time he's got to write a decent screenplay in order for the movie to have good reviews and give him credibity as a writer.
Though I will admit, he does have a thing for Hermione which in turn has hurt Ron's character, and ultimitely taken away from reasoning behind the Ron/Hermione relationship.