In our course, we do a lot of workshopping of students' writing in class, whether it be fiction, nonfiction, poems or picture books. At the beginning, we talk about what everyone can learn from workshopping properly. By properly, we mean taking the time and effort to read carefully, work out what isn't working for the reader, and then make constructive comments and suggestions. All it really does take is time and effort, even for those who have never workshopped before and feel they have little to offer.
We are all critical readers (or should try to be if we are developing our writing) - we know if a beginning is too slow, if an ending doesn't work, if a character seems shallow or if a story just doesn't engage us strongly. The key to learning is to try to work out why, and then how to fix it. The "fixing" suggestions might take a while. You might not feel confident enough to make suggestions, thinking "what would I know?" You might begin by going too far in the other direction, wanting the author to revise the story the way you would if it were yours. Finding the middle ground comes with experience.
It also comes, as I said, with time and effort. Too often, I see students whose idea of workshopping is to correct some punctuation (usually wrongly!), say "I liked this" and leave it at that. Then when it comes around to the teacher's turn to comment, they sit with mouths gaping open. Or sit with arms folded, resisting. It's a good bet that when we get to workshopping the arm-folder's writing, they will either argue or stay silent and refuse to change a thing. I've even had students who declare if no one understands what they're writing, then that's the reader's problem, not theirs.
Workshopping (or critiquing, as it's called too) can be very confronting. People shake in their shoes at the prospect, thinking they will be ripped apart. Sometimes it can feel like that! Sometimes people are not tactful and encouraging, choosing to go on a little superiority trip instead and be rude and discouraging. We try not to let that happen. But way beyond any great feedback you may receive on your own work comes a far greater benefit. Through reading and critiquing other writers' work, you learn how to critique your own.
The hardest thing in the world is to be able to get enough distance from your writing to effectively edit it, to see what's not working, to realise what it needs in order to be fixed. This comes from experience, and the fastest way to gain that experience is in a workshop. But this is what counts - you need to approach workshopping with time, effort and thought. You get back what you put in, in all senses. If others in the workshop realise (and they will, very quickly) that you can't be bothered with their stuff, you only want comments for your own work, they'll pull back and you'll get very little in return. Think of it as an investment for your future writing, and put in 100%.