I think I'll speak for many writers. YES, we DO want to know if it sucked. We DO want to know what's wrong. We DON'T want to be treated nicely. If you told us the truth, we'd re-write, get into crit groups, work on it. With this type of reply, all we can think is that you're not the right agent and we keep sending out the same schlock.
Please tell us when it's crap.
So, I've decided that either you are the most thick-skinned writer in the history of literature or you have not actually sent any of your stuff out yet.
Everybody says they can take it. I say I can, that it's not personal, but really, I'm crushed by their nice reply. G-d forbid they would have actually told me I was terrible writer the first time I tried to submit to publishing companies, when I was 14. I was a terrible writer, but at least they didn't say that, and I kept writing.
Writers DO take it personally. I know this because we occasionally receive an angry reply to our rejection, or a phone call, which is why we don't pick up the phone a lot unless we recognize the number.
Oh, and then there's Rejection Collection, a bastion of maturity and sense. Actually it's people venting their frustration, and there's nothing wrong with that, but usually they're complaining about the wording of the form letter without realizing it's just a form letter. IT'S A FORM LETTER. It just means "no." Don't try and analyze it.
Plus, I got in a lot of trouble for making a comment once to that effect, like serious trouble. The guy called the AAR and reported my boss as having bad business practices. She had to counter it. It was a mess. So forget it. I'm keeping my job, thank you very much.