I'm sympathetic to the argument but the just-so-story at the start actually made me question it. The 60s and 70s had a baby boom entering the workforce which likely led to the productivity growth rate[1]. We have less slack because it's relatively more expensive. Focusing on the cult of efficiency can distract you from the real causes

[1] "Fully Grown" goes into exhaustive research of every possibly cause of the productivity slow down. https://amzn.to/3nN1ZrR