They have a habit of presenting complicated economics in "Lemonade Stand" simplistic terms. "Labor will move to where they can make the most money, until equilibrium is achieved".
If your job moves to China, you can't move your family to China. The same restrictions apply at less restrictive levels for anywhere else.
The fact is, labor has never moved freely, and so any model built on that argument is inherently false.
The issue is that there are strongly entrenched powerful interests operating against free labour movement. Sadly, those people and organisations are themselves labelled as capitalists (sometimes, self-described).
Relocation of working-class families across the world isn't as easy as it is for a Hollywood star or a venture capitalist with fat bank accounts.
What's changed?
There aren't plots of unoccupied land in frontier territory to build shacks on, and they're not permitted to cram into boarding houses with five other families if they can't afford to rent a room in their destination city whilst looking for work there.
The developed world has also taken a lot of steps to prevent more economic refugees arriving in the country.
The huge cultural gap, and not unimportantly, the significantly lower standard of living in developing countries like China and India makes it a rather unappealing choice for Europeans and Americans.