Why did China not become a democracy to cure involution?

Why did China not become a democracy to cure involution?

I am new to politics-related questions, then please be kind if I am not asking a good question here(from your perspective). To get rid of being caught and involved in trouble I cannot not post this question on politics. Thanks in advance.

From a paper From Revolution to Involution: State Capacity, Local Power, and [Un]governability in China I read today, I learned that the central government in China has already lost its power in the 1960s by Mao and the 1970s by Deng, which can be symbolized by the crush in 1989. The ideas in the paper are based on the state-capacity-as-fiscal-extractive-capability theory.

As a Chinese citizen, I can feel a strange situation and trending that everyone is seeking his/her own interests; and equality and certainty just don't exist. Everything is weighed by profits rather than a good environment and sustainable improvement. Everyone wants to make quick money and is indifferent to others' suffering. All these lead to involution in current China and ancient China. No one is guiding the system except numbers of economic growth. It's like living in an anarchy country and history seems to rhyme again.

In ancient China, as mentioned in that paper, especially in Ming and Qing dynasties, the same decentralization inevitably appeared, and then the involution followed and then the regimes collapsed.

The author states that the endless-loop would not happen in democratic systems because of the competition and monitor between parties and because the central government is more capable and then can extract more revenue for its governing.

So, my question is that why democracy didn't appear in China to cure the involution problem? What is the prerequisite for its rise?