You don’t have to spend much time with a talkative progressive (aka liberal) to hear stories about the shortcomings of the private sector. Similarly, you don’t have to spend much time with a talkative conservative to hear stories about the shortcomings of the public sector. But the people in the private and public sectors are not significantly different. The incentives are different but people don’t change because they switch from the private to public sector or vice versa.
So we should really be talking about the shortcomings of humanity. And we should talk about the good things done by people as well. This kind of balance is characteristic of centrism. Let’s get real: humanity has a problem, called sin by theologians.
One way to deal with the shortcomings of humanity is to balance competing interests. This is what the authors of a political constitution do, or should do. The executive, judicial, and legislative branches of government should be able to correct and limit one another. This is called “checks and balances.”
When one branch of government is able to dominate the other branches, there is a problem. And when the people are not able to change the members of government, there is a problem. Yet the ability of the people to change the members of government should be balanced with the need for stability and continuity in government.
Centrists endeavor to balance legitimate but competing interests and principles. For example, a representative democracy requires equality among the people, but unlimited equality denies liberty. Similarly, unlimited liberty leads to inequality, for example, when the different abilities of people lead them to have different financial, social, and intellectual status.
So complementary opposites need to be balanced. In general this means that the best policy is between the extremes of progressivism and conservatism. But it may be that for some issues, the best answer is rather extreme–issues of life and death, for example.