...[W]ouldn't it save time for both agents and aspiring authors if the letters at least gave reasons for the rejection? ... I know agents are very busy, but wouldn't everyone benefit if they could be just a tad more informative? ...[T]he feedback we get from agents just isn't helping.
I guess my friends on the boards here have answered this pretty thoroughly. And I do understand how you feel. Sorry.
Let me add a couple of points to their very smart responses (that you will hate me for no doubt):
I am NOT a writer. I like writers, but I am not one. So questions about the specifics of craft are not for me to answer.
I am NOT an editor. I like editors, but I am not one. I think I give good notes to my clients that help their books become more salable. But ultimately, I am giving notes for salability only, not for perfection or publishability, and editing things for strangers is not my job.
I am NOT a teacher. My job is also not to give "helpful hints" or advice or teachable moments or anything else to querants.
In fact, (this is where the hate will come in):
I don't actually care whether I am being helpful to strangers with my rejection letters. I am not trying to give feedback, I am just saying "No thanks." You get feedback from other writers, from teachers, from workshops. That is absolutely not my job or responsibility.
That said, if something is very very good but I think it needs work in a specific area, I will often give quite detailed letters. Sometimes I will even prepare full editorial notes on a full if I think it is close, but not quite good enough. I don't have to do this, but it seems fair, especially if I have been on the fence about whether or not to take the thing and have held onto it for too long.
The vast majority of querys, however, fall somewhere between "atrocious" to "meh" on the scale, and I don't have the time, energy or inclination to tell those authors anything but "no thanks."