Could You Do Any Better?

In Youtube comments, I see more and more often that failed response to criticism, "Could you do any better?" -- as if only Vaughan Williams were allowed to complain about the lack of counterpoint in current film scores, as if only Kurosawa could point out the incoherence of current action sequences.

Yet I never see the obvious flip-side to this argument: "Could you do as well?" Unless you, too, are a film director, actor, writer, or composer, then you have no right to praise films, performances, screenplays, or music. So shut up!