Sociocultural anthropology, though my previous degree was in hard STEM. You (if any)?

Human/physical geography.

I said that because most leftist stuff just deals with the Economics milieu of Marx's time, and I assume (wrongly?) that Economics departments have made innovations since then.

The Economics milieu of Marx's time was Classical Liberalism (Michael Perelman's The Invention of Capitalism: Classical Political Economy and the Secret History of Primitive Accumulation is the book to read classical liberal econ). Neo-liberalism is more recent thing that started with think-tanks like The Mont Perelin Society and asshole like Hayek, Friedman and Becker (some neoliberals like neoclassical economics others don't). Neo-liberalism is more philosophical than strictly economical (The New Way of the World: Neoliberal Society by Pierre Dardot and Christian Laval and William Davies' The Limits of Neoliberalism: Authority, Sovereignty and the Logic of Competition deal with this very well, there's also Philip Mirowski's Never Let a Serious Crisis Go to Waste).