Sure, Republicans would be inept at governing for the benefit of all Americans, at solving major social problems, or at acting in a morally responsible way. But not at politics. And that's their major job as politicians. In a democracy, it's largely up to the people as a whole to solve their social problems or to "do anything of importance" in their lives.

If it were a monarchy or a dictatorship in which the leaders have absolute power, that would be different, and the head of state would have to think about more than political maneuvering to do his or her job properly. In most cases, kings and dictators succumb to temptation and act worse than politicians, which was the basis for the American experiment.