Queshire
Dark Lord
The tendency for adults to be portrayed as flat stupid (in a lot of pop culture aimed at the youthful market, not simply YA books which I have minimal knowledge of) is kind of mind-boggling in a pandering way, or as you say, the adults just don't exist.
Oh, yeah, I know exactly what you're talking about. I recently read the first book in Rick Riodan's take on Norse Mythology (the same guy that did the Percy Jackson series for greek mythology) and maybe it was just because Norse mythology is my favorite, but seeing how he portrayed the (adult) Norse Gods in that setting was rather disappointing.
Mythic Scribe
Lore Master