That’s what campaigns and debates are for. Appointees unilaterally nominated by the occupant of the highest office have no such exposure to the voting public, only exposure to scrutiny by elected representatives of the voting public. Nominees for the various positions are in line for authority delegated by the occupant holding the highest office, hopefully to administer their department from a place of more specific knowledge in these fields than would be expected from the person in the highest office. The nomination process attempts to give the nation something better than a simple rubber-stamp approval of an unqualified nominee whose sole purpose is to promote a specific political agenda.
If a certificate or license granted by the bureaucracy is a prerequisite to “serving the people”, that illustrates the problem and not the solution.