My cousin studied at Ecole Polytechnique, then did a phd at another top french school and become a professor there.
He has 6 articles publishes in the top 3 Math/CS/AI conferences.
He was literally paid 45k€ a year, before taxes and other things, that's 2300€ a month after taxes, his rent was 1100€ because it's Paris, now Polytechnique has one of the hardest math/physics entrance exams in the world, and he published more papers and in more prestigious conferences than most of his colleagues.
He took a couple months to leetcode then got the fuck out to the US, his salary now is legit an order of magnitude higher than what it was, doesn'r have to think about food, transportation, still gets to do research, etc.
I mean you can be as patriotic as you want but when it's that different who's gonna stay here...