I get the idea. But it means folks learn on the job.
A political party has the ability to limit the selections to folks who have useful experience. If Oprah wants to practice, tell her to solve Illinois' issues.
Our csl says that the Dems there could use some housecleaning. If she can clean that stable, then consider the presidency. If not, understand that the job of being president may be too hard for you.
When making tv shows, the job is to be popular. When being president, it's to do right things even when they are not popular. How many celebrities have a training in being disliked?