Since we are talking about Marxism, I think a handy thing to point out is that Marx advocated for revolutionary governments to nationalize only the large firms and key industries, and keeping private property for the smaller ones to allow them to develop more rapidly. Marx made it clear that development of the productive forces is the primary task of the revolutionary government, and that public ownership and planning works best at these larger firms.

Marx believed you couldn't get rid of private property by making it illegal, but by developing out of it. Now, that doesn't mean that you can't go for a more publicly owned economy like the Soviet Union was, but if we are speaking about adherance to Marxism classically, the PRC better fits that. The large firms and key industries are overwhelmingly publicly owned and controlled, while the private sector is dominated by underdeveloped small firms, cooperatives, and sole proprietorships. China has uneven development, and rapidly developing the rural parts of China has been a key focus in the last decades to counter this unequal development.

Awoo's comment is also good information as well, even if we wanted a fully publicly owned economy in China now, they would still need to have trade with other countries for key resources and thus commodities to trade.