Indeed. I've had a problem or two with people who say, "This, this, and this are wrong," but offer no useful suggestions on how to "fix" it. But those have been very few and far between. Most people in the industry, if they have the time (and not all do), will give honest and fairly objective suggestions. (And by objective, I mean discussing technique, or how to draw anatomy if you're attempting realism.)
Sometimes their advice may sting, but don't ever get defensive about it. If they didn't care enough to want to help you do your best, they wouldn't say anything at all.
And because they're only suggestions, you're free to not take them if you don't think they'd improve your work any.