I recently wrote this in the comments section of a blog post wondering why editors and agents don't give more specific reasons for rejecting a story:
I'm an editor at a smallish zine and I'm not half as busy as the folks at SF&F. I still don't have much time to write anything personal on my rejections. The sad fact is, my fellow editors and I are interested in making the best zine possible, so we put most of our time into the writers and stories that make it so.
If you get a personal note from me, it means your story was damn good, just fatally flawed in some way. I always do my best to detail it in a sentence or two if I really liked it. But understand, that's for about two stories a year. (note: and Electric Spec doesn't accept resubmissions) The rest of them get the form letter.
The sad reason we on the recieving end of writing often don't detail our thoughts is because at some point it's inadvertently invited a conversation with a writer desperate for critique. (I admit I've been on both sides of this table.) I already give much of my time to my two crit groups, http://crapometer.blogspot.com, and sometimes to fellow bloggers. That's the time and place for it, not at my zine.
Critiques come from critique groups. Unexplained decisions come from editors and agents. Unfortunately, we're in a competitive business.
I don't exaggerate when I say I put in a lot of time critiquing others' work. I recently posted on this very topic. Fact is, I love it. I think it makes me a better writer and reader, it challenges me to stay at the top of my game, and some of the very best things I've ever read I've found in the process of critiquing.
But I can't critique the stories I get here. Example, right now I have likely 40-50,000 words in my inbox right now. I do tend to read stories to the end, somewhat compulsively, and I do keep a running crit going in my head while I do. But I can't write those critiques and have much time for anything else. I wish I could. I'm not much different from any other editor out there. If you get a critique of your work from anyone in a position to get or give you money for it, consider it a grand complement, consider what they've said carefully, and then move on.
side note: if you're interested in a crit from me, Crapometer is the place to go. It doesn't mean that I'm going to buy your story if you do everything I say, but I think you'll get valuable advice there. You might consider it a back door entrance to my inbox. I've already requested one story from there. Just note that I didn't ask for any changes when I did.