Read on. Dumbledore is clearly one of the smartest characters in the book, not a drooling moron at all. He puts on a pretence of being completely bonkers to confuse his enemies, but he's very smart and thinks fifteen steps ahead (just one short of Harry...) and is one of the few characters in the book who's an Agent rather than an NPC.
As for the other characters, their level of agency varies, but at the very least Quirrel, Hermione and Draco are also agents (i.e. smart enough to be capable of driving the story in a meaningful way), and the other characters are portrayed fairly accurately given their stupidity in the original books.
In the original book, ALL the characters are stupid. In HP:MoR, 5 characters are not stupid. I think that's an improvement.