Wanting a philosopher king isn't a bad idea if you aren't mistaken about the philosopher king in question.

Or about your definition of "Philosopher king" in the first place. The character of Marcus Aurelius fit the preferences of those in Rome who dreamt of such a philosopher king; yet he was a poor ruler who displayed apathy - including going against his moral intuitions so as not to actually do anything, like finding gladiatorial games distasteful but making no attempt to limit them - and mediocre crisis management