Democracy and prosperity are not strongly correlated. Certainly some of the wealthiest populations and individuals are to be found in Hong Kong, Mainland China, and several Sultanates. There are many democracies that endure grinding poverty. Countries with some of the strongest democratic institutions have seen  vast wealth centred in the hands of a tiny percentage of the population (1% is an exaggeration - it's fewer than that).

Prosperity and good governance are complex notions that preclude a blind faith in the notion that democracy is 'the answer'. Have a look at the Legatum Prosperity Index for a more nuanced perspective.

The best argument against the democratic system is to spend 5 minutes listening to an ordinary voter. Ponder this: democracy is what brought us the Trump presidency.