Yes, and that is the crux of the discussion on this thread, that democracy alone is not sufficient, but a Constitutional limited government which identifies inalienable rights, with limits on power, is necessary. The preference for a changeover of leadership which is instituted by our Constitution, recognizes the innate tendencies of human beings to retain power, ala FDR who did not recognize the precedent set by Washington.
In the long run you are right: a constitutional government is always optimal. However, it is often necessary for a primitive society to go through a period of benevolent dictatorship before it can adopt constitutional government. Constitutional government requires certain instutions, such as rule of law, and civil habits, such as respect for private property, that a primitive society lacks. Hence it is necessary for such institutions and habits to be imposed by force by someone like Ataturk or Pinochet or the Shah.
In addition, the long-run constitutional government need not be a Republic. For some societies, a constitutional monarchy is preferable.