Neil DeGrasse Tyson likes to remind us that "culture is what you don't notice." You might see PRC Propaganda in this description of Cixin's work, but if you think about what movies like "American Sniper" and "Top Gun" and the Superbowl must look like to non-Americans, then "propaganda" becomes a relative term. I have long been under the impression that Chinese culture is heavily censored and controlled, so I am perpetually amazed at the things I find portrayed in Chinese media, like the reoccurring themes of government corruption and the importance of a strong press.
I just finished reading The Three Body Problem, and I did not see anything propaganda-like at all in the book. Cixin presents some pretty complex moral issues for the reader to wrestle with and an extremely damning portrayal of the Cultural Revolution as being anti-science, anti-intellectual, and horribly destructive to the environment. The book opens with a physics Professor on trial for the crime of teaching modern physics, which is considered Western propaganda. Later we see the Cultural Revolution slash-and-burning entire forests and turning them into deserts and one of the characters gets hold of and is influenced by Rachel Carson's Silent Spring, which is banned by the government for pushing capitalist ideology (how ironic from my American perspective). It is only decades later, when China experiences a renaissance of free public education and science that things are portrayed as getting better.
In fact, part of the aliens' plan to keep humanity weak is to undermine science and promote magical thinking in our culture. Despite the seemingly pro-environmentalism message early in the book, the aliens consider using environmentalism to halt our scientific progress. The reader is left to thinking about how we balance scientific progress against extreme environmental crimes like those committed during the Cultural Revolution.
The bad guys in the book are a cult of of human beings who want an alien race to provide a central totalitarian government to the entire world. That doesn't exactly endorse central planning. The book portrays overt nationalism as detrimental and unsophisticated, as when a proposed nationalistic message to extraterrestrials is scrapped for a universal statement about humanity.
I'm sure there are ways to interpret Cixin's writings as PRC Propaganda, but--like most complex texts--there are ways to support many criticisms of the text, even contradictory hypotheses.