When I look at our government now, and all the work they're doing it makes me totally understand how Rome went from a republic to an empire. I mean, god fucking dammit.
Anyway, a Monarchy would be a very efficient and beneficial form of government provided it was headed by a strong and wise ruler. By nature of their position they could afford to make some unpopular but necessary decisions that elected officials in practice will just never make. Elected officials put off short term pain to ignore long term problems. A monarch might just weather a grumbling populace for few years until they either forgot about the problem or his wisdom became clear. Politicians who promote such ideas will be voted out post haste and replaced corrupt and incompetent worms that spew what the stupid populace wants to hear at any given moment.
The trouble is, even when something close to one of those happens along they tend to eventually die which leaves a power vacuum that will statistically be filled by your average piece of shit. And the trouble with a total monarchy is it is a very efficient form of government! That piece of shit can then fuck things up seriously bad really fast. And since good leaders are rare, its really a net negative.