Is it better to know that the photo sucks for unknown reasons, than to maybe think that it's the bee's knee's? Hell yes!
This is where I tend to disagree.
There are many here who have no clue...me included.
When someone says the photo sucks and does not provide even one reason, that is not acceptable to me.
Tell me it sucks because of color, composition, focus, wrong aperture, etc... and now there is a reason it sucks. I do not have to like the reason, but give me some direction. If you provide me with a 'term' as part of the response, I can google it and try to find more info...I do it all the time
I am an expert in my field. One of the reasons I have the reputation I have is because I provide an answer. There are many times they are not happy with the answer, but they are always content they have a proper answer. And how do I know that? They keep asking.
So, if one wants to say it sucks and not provide a reason, that person is just vindictive (that is my opinion).
If one does not want to provide an opinion, then do not respond.
I mean how hard is that????
One other issue that has already been mentioned, but I think deserves more ink.
This forum cover a lot of geographic territory, which is a really good thing. But, we are all different, and a response can easily be misconstrued just for that reason.