[PKop]

The low birth rate is a macro phenomena in response to massive population boom and limits to growth, a significant one being living space.

Packing even more people into these nations, with the added political tensions of making them foreign immigrants vs domestic growth of native population would exacerbate the original problem with added downside.

Look at the density, cost of living and other factors that flow from "too many people in one place". The natural counter trend must run its course.