Some can't read. Some can't remember. Some can't improvise. Some don't have a good technique. (And not just, as Backwoodsman has said, only in music). And probably we're all in there somewhere.
But - with apologies to the religious:-
"If anyone causes one of these little ones to stumble, it would be better for them if a large millstone were hung around their neck and they were thrown into the sea."

Surely our purpose is not to be entertained, and to criticise those who don't come up to the mark (those who think theirselves good should be the entertainers); but, while enjoying the good, to encourage the less competent to improve their performance, not to complain about it; however trying it can be at the time.

Those who are able can take pleasure in what they do well, and hopefully give pleasure to others (don't you just love to hear those feet tapping?) But don't condemn those who don't have your abilities.