Sometimes people don't give feedback if we don't like something. They don't want to be mean. They don't want to start up any drama. Maybe some folks just want to be liked and are afraid negative comments will cause problems. Maybe some people are afraid of making enemies or sparking a conflict. For some it isn't worth the time to try and hash it out on paper why they didn't like it, what they felt was missing, etc etc etc.
I think if an artist wants real, honest feedback the internet isn't the way to go. I think that art classes where folks are actually showing up and making the effort is a better place to look for constructive criticism. I got next to nothing on my short stories posted on DA. Two people made an attempt to be constructive. But in a writing class I got loads of immediate feedback and it was really helpful. It was face to face, it was a class of people who were all there for the same reason, and it was professional. I think that DA is a big posting-board for amateurs. There is some really nice stuff there but mostly it seems to be an "art-focused Facebook." I think serious artists would be better off elsewhere. Some people have done well and have developed a following so it isn't all bad.
I guess my last thought is that we're generally not as good as we think we are. I certainly learned that after taking this class and went back to the drawing board to develop better skills. My so-called writing needed mega amounts of work. Still does. Unfortunately a lot of people have inflated views of their creations. Whether it's a clumsy short story, a poorly sculpted doll, a face-up with the worst gloopy paint ever, or a web comic with no real conflict or story happening we might think it's awesome cause we love it and we've worked hard but... eh. You know. It might just suck. Maybe we can't see it when we suck. We don't want to see it. One of the best blog posts I ever read was titled something like "nobody cares about your story," or something like that. Wendig was the name of the guy who wrote it. It was a great post about getting over our egos. If I can find it I'll link it cause it was pretty awesome.
But like you guys said, without constructive criticism we'll never really get that 3rd party view will we?
/headdesk.