He's an idiot. He wastes pages and pages on random crack-ass subplots that are direct results of his idiotude. And puts the kids at risk, because he is an IDIOT. Harry, Ron, and Hermione are always "oh, no, we have to help/save/reinstate Hagrid after his monumental idiotic failure!" and I'm going "NO! CUT YOUR LOSSES, SAVE TWO HUNDRED PAGES, AND RUN!"