There is the CCP. They've gone around indoctrinating everyone for 70 years that Mao was the messiah, Xi is Peter the apostle carrying on his vision, and western democracy doesn't work. Removing that would be a huge shock to the Chinese public (Destalinisation is an example of what happens when you remove the cults of personality), not to mention the existing power structures holding up the state would need to be reformed. I believe nothing short of another civil war will bring democracy to the PRC, and believe me, a civil war in China will be bad for the entire world. What I talked about before was before the CCP. Times were different, and the party that at least pretended to be democratic (the KMT, who proved themselves to not be democratic on Taiwan) had a chance to win the civil war. Today, there are a billion more people in China than when the KMT left, and not very many of them believe in democracy. It's not impossible, only mind-numbingly improbable.
Taiwan is a special case because it came after years of KMT oppression and the death of Chiang. His son was more lenient and then his son's successor opened the door for democracy. Taiwan is much smaller and had more exposure to America than the mainland, which definitely helped.