Competence is enough. Competence is all there is.
As a practicing and performing musician and as a composer my first goal is to be competent. Of course I would love to be more than competent, but I don't have a great deal of control over anything besides my daily work--moving one step at a time. Anything beyond mere competence that might happen to come out of me happens on an subconscious level, and no matter how hard I try, I have no control over what happens beyond competence. I have no understanding at all about how subconscious artistic stuff works. I'm really happy when it does, though.
As a critical listener (and as a reviewer) I am usually not impressed by competence. I can even be bored by competence, which is odd because I know how much work goes into writing a competent piece, giving a competent performance, or making a competent recording. As a critical listener I can tell when there is something special going on, and I can be impressed and even moved by a performance that has audible flaws. Clearly Hewitt did not intend his maxim to be interepreted by an audience of critics.