By failed “international class war” do you mean like establishing an international and trying to do a global strike? I think most people have abandoned that strategy besides maybe WWP. As for China being socialist, even they don’t claim they are. I’d describe them as a mixed economy under a proletarian government. I’m not sure why you suggest a socialist country would try to sharpen contradictions. As I’m currently reading ‘The Correct Handling of Contradictions Among the People‘ it appears to me that the CPC is treating the contradiction between the proletariat and bourgeoisie internally as contradictions among the people, as they already have state power.