Are you familiar with the throwing a brick thread? It is for the weekly challenge and you leave a link to your piece and ask for feedback.
If you want detailed feedback, you should check out the Critique Circle.
I try to comment on as many pieces as possible and have found in return, people leave me critiques. Often, I'll click on someone's name who has left me feedback and will leave something for them.
Another thing I do is have my signature included on every post, so people, e can click on Shane's profile and it will take them right to my page with all my work on it.
Unfortunately, some people have been skittish about leaving constructive critiques because some people get quite upset. Though I always make a point to say more positive things than negative, I've inadvertently hurt people's feelings. I've had people say I'm the reason FW has gone downhill, they will never write again because I ruin their passion, and that they are leaving FW because I obviously don't think they are talented. This crushed me each time. I'm not the only one who has had hurtful remarks and it's not easy to take when I'm truly coming from a place of love and a genuine desire to help people become the best writer possible.
Also the suggestions on how to leave and receive a critique can be found in several places on the main site. There is a spot both in the Critique Circle and in the weekly challenge as well as some other spots too.
So before you give up, try the brick throwing
if you have a challenge piece, or the Critique Circle
or the Open Forum and ask for feedback for a general submission piece (leave a link) also if you need help with adding a signature, check out the FAQ