Is it impossible to get valuable critique on such a forum?

The contest pitfall on this board that I see intermittently but often is that a mediocre photo will be put up over a better one, which is then passed on to the next aficionado of mediocre photos, who will then, etc.

Criticism certainly helped me up my game.  It stings, but can be helpful when you take it and make improvements.  After a certain point, you become secure in your craft, don't give a damn about what anyone else thinks and don't ask :^)