True, the social dimension of most sites has mostly eaten alive the value added part.
Now, to be fair, the more advanced you are, the more complex it becomes to provide criticism that is really useful to progress. I am focusing here on people that have a reasonable chance to remain photographers in the long run.
It is pretty much a given that everyone's technique is flawless and that our gear is not limiting us significantly, right?
So moving forward can typically only be enabled by discussions about vision and intent that end up not being related to the physical act of capturing an image. That frustrates more than a few photographers who are addicted to the physical proximity with cameras and gear.
The best advice that could be given to many people asking for real criticism may be to stop taking photographs for a while, sit and think.
The beauty that we are somehow all seeking to generate is mechanical in parts, but at the end is never quite successful unless there is a powerful underlying thought process. Commenting on a single image is rarely useful and I would go as far as saying that asking comments on a single image without providing visibility on the why is pretty much useless. There, I said it.
Cheers,
Bernard