The article mentions globalization but doesn't view inequality through a global lens. If you look only within rich nations, yes inequality has increased, because the poor and blue collar middle class have lost a lot of jobs to poorer countries. But that phenomenon is actually reducing inequality as measured from a global view.

The biggest issue I have with the article is that it ignores the geopolitical trends that were actual checks on inequality historically. Inequality typically only decreases in the face of an existential threat to the wealthy; when the US passed 90% marginal tax rates, it was to fund a war where the ability of the wealthy to remain in power at all was in question. Getting pensions and many other social democratic policies which benefit the poor and middle class, in many countries in the world, often required blood instead of the free market.