Dictators absolutely don't have absolute power either - they have to juggle it with the military, the private sector, and so on, at the very least. In practice, the concentration of power between a dictator and a monarch is very similar. There are monarchs that hold a lot more power than the average dictators, and dictators that hold a lot less power than the average monarch (Marxist-Leninist states such as the USSR or China have their dictator share quite a bit of power to the Politburo, lower cadres, and so on, for example).

In general, monarchies pretty much have had the absolute maximum of power concentration possible without disastrous consequences.