Global society has indeed become far more efficient today than in the 1950s. That's precisely why a working class job no longer affords a middle class lifestyle

Global society has indeed become far more efficient today than in the 1950s. That's precisely why a working class job no longer affords a middle class lifestyle. All industrialized countries except the United States were physically destroyed by World War II. The US was the only place where any significant amount of industrial infrastructure still existed, so the US had a massive postwar economic boom as the nearly sole supplier of industrial goods as the rest of the world lay in ruins. American workers thus enjoyed a brief period where a basic working class industrial job could pay for a middle class lifestyle, entirely due to that inefficiency. Nowadays, things are far more equal and efficient globally. American workers no longer enjoy exclusive access to industrial infrastructure, so having a basic job once again yields only a basic lifestyle.