Nah.. not really. I'm sure there were plenty of ancient leaders / policies just as stupid (if not more) than many current ones.
Also, a leader being stupid might actually be better than a smart one that is a sadist and has all the power that leaders used to have in ancient times (Roman emperor Caligula, for example, is famous for being crazy cruel... or people like Ivan the Terrible).
Also some were outright mentally sick, probably helped by the inbreeding that usually took place amongst royals.