i disagree, there's absolute nothing preventing an ordinary Chinese from taking a exam and become someone that actually has influence over domestic policies. Elections aren't the only ways a legitimate government can be formed.
Don't think joining a party with clear views and goals would let you have any significant effect on its trajectory without decades and lots of luck.
You might be able to become a social policy research professor or something, or where you study Communist/Marxist/Leninist/Maoist/Jinpingist/etc thought and try to develop new applications of it to the modern world. But you won't get to change anything from the Politburu, and could lose your career or worse if you try.
[1]:https://en.wikipedia.org/wiki/Politburo_of_the_Chinese_Commu...