We've got warring notions of "competence."

You're talking about the "competence" to achieve one's political aims; the ability to get laws passed, for example, or to administer programs. This is bad in the hands of one's political enemies -- it is not good when Nazis are "competent" at genocide.

The OP is talking about the "competence" to achieve those goals where everyone is in rough consensus -- we all want GDP growth, but the most competent politician is the one who's best at getting it. This is usually less a matter of being good at getting laws passed, and more a matter of judging the efficacy of policies against the real world.

This kind of "competence" at non-controversial goals is universally a good thing. Nobody wants the trains not to run on time. The question is, would you prefer a politician who's competent at non-controversial goals, or a politician who's on your side in the controversies?