Ratemyprofessor is, at times, overrun with malcontents and trolls, so I don't find most of the reviews useful. I work for a University and was researching our "competitors" to see what was being said about their classes. "Boring" was the single most common remark for many of the professors. I would expect an engineering professor to be less than entertaining...maybe they should learn to juggle, lol.
I don't think that an anonymous coach rating site would be useful, especially given the dramatics that accompany figure skating. We've seen posts on the board in the past, praising new coaches to high heavens for a short time, then bad-mouthing them later after things didn't work out. Plus, it wouldn't help anyone just starting out because they wouldn't be able to find it. Look how few people know about this site, which has been a mainstay since 2002.
So, I respectfully disagree with your opinion of the value such a site would bring to figure skating. It would open the door for more mockery and pranks, imo, without professional moderation and control.
However, I do think a professional survey-based evaluation, such as the Princeton Review provides for colleges, would be useful. If we could keep out posers and troublemakers from completing the anonymous survey, that would be the best solution.
I just received a survey request from the USFSA, asking for feedback about the Synchro Sectionals competition I attended last week. I haven't responded yet, but it might be a template to consider.