Indeed this is what the article concludes. The last paragraph says, Nagel concluded that democracies rarely or never elect the best leaders. Their advantage over dictatorships or other forms of government is merely that they "effectively prevent lower-than-average candidates from becoming leaders."
A republic is all about establishing a reasonably strong mean, back to which a succession of various administrations tends to revert.
Other forms of government allow for much higher variance. You might get a brilliant and benevolent monarch, for instance, but his son might turn out to be incompetent or tyrannical. In which case, sucks to be you. Hopefully the 30-year dice roll turns out better with the next heir.
