While there was pressure from the outside, outside pressure did not kill the USSR. China changing since the time of Mao is a given, even if they followed the path of the Gang of Four to today, this would still look radically different from the era of Mao simply due to economic development. China of today is still a socialist economy. The DPRK survives because it is heavily millitarized and focuses on economic independence, with nuclear deterrence. Vietnam and Laos are both doing well as well. Cuba is still trucking along.

As for "subjugation," I think it's better to understand why this happens and for what reason. Capitalist states eventually see a merging of bank and industrial capital, creating finance capital, and this monopoly stage of capitalism is what drives imperialism. Socialist states do not have such an economic drive. While conflict persists, there is more of a drive for cooperation, consolidation, and increasing sovereignty. This is not "Utopian," this is the recognition that centralization of production is economically compelled, which is why States have largely merged over the years, similar to corporations.