I was introduced to Robert Cox back then in my International Political Economy class and now I'm revisiting his work under the Marxism chapter in World Politics class.
Current Marxist schools of thought are difficult to define because there are so many branches, but most of them can logically lead to this 'supreme' conclusion that spectacularly takes out its intellectual rivals, Realism and Liberalism, at the same time.
"Global acceptance of neo-liberalism is very much in the interests of the developed world and has involved a large degree of coercion. That such policies seem 'natural' and 'commonsense' is an indication of the hegemonic power of the United States." Thus, Realists have become liberals when they advise the US government to push for the Washington Consensus on free trade and liberalization in order to sustain the US's power in the international political arena. On the other hand, Liberalism has simply been reduced to a tool as Realists seek to preserve the prevailing order.