Most of human history, the monarchy has been depraved -- even Catholic or lutheran or Calvinistic or Anglican or Moslem or Hindu etc
The best form of government is a republic during peace times and a dictatorship during war. This was clearly apparent in the Polish-Lithuanian commonwealth where the King was powerful but not all powerful and while he could not be deposed, he was elected by the barons
I would not want Obama as King. I would not want most of the Spanish monarchs as king either
the Spanish weakness is more an indictment against welfare state policies (which are intrinsically leftist) rather than about monarchy or not
What government to have during peace is a moot question. Any will do, the less the better and none is the best. Beyond a judge and a police department, -- which can be wholly private, -- no government is needed and most is harmful in peace time.
Given that most countries either are at war or prepare for one most of the time, the choice of a "dictator" as you put it becomes important. Here the contrast between a dictator without a legitimate claim to leadership and a monarch who simply owns the loyalty of the force and the military infrastructure could not be clearer. A gifted field marshal a dictator can be (Napoleon Bonaparte); a man whose life long duty is to defend his people, often against his government, that is a monarch, -- he cannot be.
Now would you rather have a man skilled only in lying in speeches and charming the press, yet democratically elected or a king whose rights to the throne no one disputes?
Which brings me to the Carlists. They have one point: you cannot get a king by altering rights of succession to suit the moment. Yet that is a force that rose to defend their country a hundred years after the Carlist controversy began and no doubt, if Spain calls them, will take up arms again. That is the power of the monarchic idea. It is worth many divisions, and many elections.
Confusion between other forms of non-democratic leadership and monarchy is unfortunately common as a result of pro-democracy myth-making.