I don't get many critiques on the images I post, but then I also don't ask for them. So this is a comment that would be directed at others who look for critiques. What I personally find frustrating are the critiques that have nothing to do with the image as a whole, but a nit pick on one element that has no baring one way or the other. Many critiques are coming from less experienced people, but they feel adding their own pointless thoughts is going to help. It is difficult to critique some images without knowing what the limitations were when the image was shot, an example being "That photo would be much better if you moved to the left 5 feet" the problem being that 5 feet to the left, is 4 feet off the cliff.
I offer suggestions based on my skill and experience and understand that without myself standing in the same place, working with the same light, I don't know if the image could be improved. I think this is also where less experienced people offering up critiques can annoy and upset the photographer. I don't have a problem telling someone that a picture is really very average, or should not have kept as it isn't sharp, if the technical side of the image fails drastically, but I will give a reason.
Most of the regulars on here know that I don't back down when I make a statement about an image, most people appreciate what I say based on my experience, just as I read critiques one here by others that are very well stated and helpful. When there is confrontation because of a negative, but useful critique, it usually becomes a personal battle from someone that has their own skill issues. Not every image shot is amazing and people should never expect to be told that. I have learned over the years that I have probably produced more average images than anyone else on the forum, based on the hundreds of thousands os images I have shot.
I've had my images critiqued by my Dad for decades, I didn't always agree, but deep down always knew he was right, and I learned from it. As long as we learn from a critique it doesn't matter if it's positive or negative.