There are dozens of reasons a query might be legitimately (and quickly) rejected, only some of which involve the actual quality of the work.
There are things like the length, the subject matter, the target audience, and lots of other things that can be picked out of the query letter in a very short time.
Slush piles, in this Age of Digital Writing and Submission, are now slush mountains. It takes very, very little to get rejected today with so much to go over and so much to pick from.
More on this from
Lynn Price's blog.
Keep trying. Something that one agent or publisher has no place for may be just what another one needs. This business is a lot like dating--there's really no way to tell ahead of time when you're going to hit it off.