Oh, the dreaded "?????"
On the face of it, it might seem like the least helpful critique comment you can receive. But I disagree.
So many other areas of feedback can be a matter of taste. One time, I got two different critiques back at the same time. One highlighted a section and wrote, "Pick up the pace here." The other marked the same section, "S-l-o-o-w down."
But if I see "?????", I know an area needs a major overhaul. No ifs, ands, or buts about it. Because I'd rather have a crit partner say it than an agent.