Yes, we have had a few different incarnations of a 'critique forum'...and in each case, there were enough problems that we had to change it or just take it away.
It started with a simple critique section where you would post a photo and ask for critique. The problem was that few people provided any information to go along with their photo, so it was hard to offer any useful critique because we didn't know if the photo accomplished what the photographer wanted. You could say "it's under exposed"...but maybe that's the way they wanted it.
On top of that, most of the comments were still useless dribble like 'Great shot'.
We had guidelines. Only one photo at a time, provide some background info etc. But only about half the people followed the guidelines.
We also tried rules for the comments, where useless posts would be deleted. That didn't go over very well either.
We tried a much more structured format, where threads & comments would be out-right rejected if they didn't meet the criteria that was set out...or they would be edited so that they did fit. People really didn't like that.
We tried having a committee, made up of both mods & regular members, to figure out the best way to make a satisfactory critique section. That didn't work either.
Now we just have gallery sections....and if you want some critique, you just have to ask for it. As pointed out by someone who would know, most people don't really know how to properly ask for critique and even fewer actually know how to properly give critique.