Let me honest- I hate polite writers groups. I really dislike the workshipping process where only constructive feedback is given. Frankly, I want to really hear when some thinks that what i do is not working, is wrong, or just stinks. I have learned, of course, that many others do not share my desire for brutal honestly, so I heave learned to modify my feedback to the most strengths-based way of saying things.
I do believe, however, that if your ego can take it, ask your mentors or colleagues to be a bit more direct than they may be being. It will save you a lot of time trying to decipher when “I am not clear if this section is meeting the aims of your paper” really means “I have no idea what you are saying here.”