People say things like "Stop criticising when you can't even do it yourself." I thought, why not? If I know what standard it should be performed at, if I can point out the mistakes, if I can correct you, why not? So what if I can't do it myself? The point is, I know the way it should be done; I can teach you; I can bring you up a level in performance. So, why not?

It simply occurs to me: Do critics really excel in that field themselves? Or do they have to be?

Is the best basketball coach the best basketball player? Do the novel critics write best-selling novels?

No.