I think it helps to have forms they need to complete as they're critiquing each other's work. That way, they have to directly answer the questions or underline the thesis statement.
It's important to be clear with your expectations. If you make it clear that "it's good" isn't enough and have students explain WHY it's good, then they'll at least have to think about it.
Even if the feedback isn't quite as thorough as you'd hope, I think it always helps to have students see each other's work.
Then, at least they get a chance to see examples of how other students on their level organize their writing.
I think it helps to have forms they need to complete as they're critiquing each other's work. That way, they have to directly answer the questions or underline the thesis statement.
It's important to be clear with your expectations. If you make it clear that "it's good" isn't enough and have students explain WHY it's good, then they'll at least have to think about it.