Idiocracy is not a good movie, if you are watching it like a regular movie. It must be watched for the subtle jokes, and if done properly, the brilliance is revealed. Part of me thinks the editing was just bad, but another chunk thinks Mike Judge did that on purpose to prove a point.
As for why it was not marketed: if Americans understood half of what that movie lays forth, most large corporations would go bankrupt within hours because nobody would put up with their huckstering any longer. Maybe I'm giving too much credit to the average dullard, but I do believe that.