(A) social media doesn’t grant any new insight into the living conditions in attractive countries. That’s been apparent through media and communication for decades.

(B) migration is hugely asymmetrical. Many people want to come to the high status countries, few want to come to the low status countries. Borders tend to be enforced more strictly when there is higher demand for entry. So in a world with clear differences in quality of life between different countries, borders aren’t going anywhere.