Why did the four great thinkers in Qing Dynasty (Li Zhi, Huang Zongxi, Gu and Wang Fuzhi) critically inherit traditional Confucianism? What is the basis?

Critically inherit, their theories are all innovative and developed on the basis of traditional Confucianism. For example, the people-oriented they advocate belongs to the category of Confucianism. Their criticism is based on inheriting traditional Confucianism and criticizing Neo-Confucianism in Song and Ming Dynasties, which is understandable. Neo-Confucianism in Song and Ming Dynasties is only a part of Confucian system.