In a country of 1.4B not everyone is going to agree which is evident in US w/only 1/4 of population. Chinese are free to immigrate elsewhere if the choose to do so.
Chinese citizens elect leaders at local level who in turn elect those above them and this continues to the highest levers where only the most competent rise to the top.
Communism is a misnomer when applied to China. It is no more communist than US is a democracy. In fact in many ways China is more democratic than US whereby it's govt of 90M+ members more accurately represent interests of Chinese society.