Those countries could keep their own talent through economic policy (i.e. fuck you pay me)
That they don’t is entirely their own fault and they deserve to be brain drained. “Talent” are people with agency and not possessions subservient to national interests.
no, there are already runoff places that will brain drain the rest. there will be no "great repatriation". it's not just "The US" and "Home", there is an ease of immigration, quality of life, and success potential gradient.