[dragonwriter]

> I subscribe to the idea that the most important aspect of democracy is to be able to kick out the incumbents

In think you are wrong on both points. The most important aspect of democracy is that it produces a government that reflects the popular will; being able to throw out the incumbents—at which the US does exceptionally badly—has some instrumental value to that, but isn’t an independent goal. And the pervasive use of FPTP elections is a big part of why the US is bad both at tossing incumbents and at providing effectivelt representative government.