Your theory of politics is wrong
A democratic polity does not elect a technocrat-in-chief, but politicians whose role is to define priorities that must later be translated into well-crafted policy details. Paul Ryan’s various budgets haven’t been wrong because they require giant magic asterices to make the numbers add up. They have been wrong because the interests and values Paul Ryan represents are wrong. The magic asterices don’t reflect dumb mistakes, but smart politics.
.. expertise on technocratic matters ought not translate to any deference on interests and values
.. If you are honest, you will follow your own theory where it leads, as Bryan Caplan has, and work to limit democracy. But Caplan, whom I love, is mistaken, because he begins with a mistaken theory of politics. If you want to see how that theory of politics works in the real world, look no farther than the European Union, which is a real-time experiment in demoting democratic adjudication of values in favor of technocratic adjudication of facts.