Economy is strong under competent management, and weak under incompetent management.
Under democracy, the incompetent officials call be changed to let others try.
Under authoritarianism, those who speak again incompetent officials get silenced, and the everyone is stuck.
Democracy is not about being strong all the time, we already know such thing is impossible due to external events: trade partners recessions, trade disruptions, trade partner currency swings, large natural disasters. It prevents anyone from monopolizing power and using that to have everyone suffer from their incompetence for lifetime. (Also known as “Bad Emperor Problem” in context of Chinese history).