Totally agreed. I have long been trying to figure out how an incoming graduate student may assess the quality of a professor beyond his academic publications and asking people who work with him. I have come to the conclusion that the best predictor is reputation amongst peers. I may be wrong here, but from what I have seen it usually is the most accurate. The issue is that there is no review site for professors outside of their teaching inside of classrooms. Would be very helpful in selecting mentors, imo.

Maybe even a matching market, much like medical residency in the US.