I was a graduate student in one of the best institutes in PRC in Beijing in early 1980s. To my psurprise, the insitute was almost empty in terms of reasearch although it is the best in China in the area.
Some senior people were highly respected since they were educated or studied in US or Europe or Japan before early 1950s. But they were too old already. Their research was also obsolete.
People who were graduated between 1950 and 1966 had very limited acievements. Then it was people like me who were fresh graduates.
I am not a politician. But I can share a little story. Chern SS gave some lectures in Beijing in differential geometry in 1980s. The audiences were the best faculty of China at that time, but no one understood him (people even didn't know the symbols on the blackboard Chern SS wrote).
Just remember, from 1949 to 1976, almost no one had good opportunity to study or to communicate with US scientists. How can people do good research?
Basically, my professors in Beijing learned things just a few years earlier than I did. Gradually, we can do some research.
If Mao lived till 1986, I am sure that things will be much worse.
If you believe that Mao is GREAT, it is fine. This is just what I saw,