The close reasons ("too broad" and the others) are good descriptions of the typical bad questions. Anything which doesn't fit into any of the dozen-odd close reasons is not typically a bad question.

This summer I waited on a lot of six- and even twelve-minute batch jobs, and I spent some of those on the SO moderation queue (I'm one of the 3000-karma users, not an elected moderator). It didn't take much more than six minutes to learn that picking the interesting questions out of the flood of manure is a terrible chore.

It would be nice if the intellectually interesting questions could be left alive. But I don't think it's humanly achievable. People will post their job interview quizzes and first-year CS exercises and say, oh, mentally stimulating and please do leave open.