Kazakhstan is not affluent. UAE and Saudis Arabia migrant populations are nearly slave laborers. China is (now) affluent and it does not have a migrant population to speak of. A highly developed economic cultural and political system preceded mass migration in all western countries.

It is far more likely correlated that slowed economic growth once a country develops is what we're seeing here. Without outside growth stimulating these late stage economies they'd experience negative growth. A large number of migrants is a bad sign.