Earlier quoted context omitted.
That's not how it works, not everyone wants to move country just for a (way) better salary.
There's definitely an IT brain drain in France due to low salaries, very few people of my former school actually work for a french company anymore, they almost all went somewhere else to get a better pay. In the post-covid world of increased remote working, the brain drain will likely increase tenfold since developers won't even have to leave the country anymore.
If I, a french worker, stay working in France, I pay French taxes and my lineage and social impact remain in France. I can't imagine how that is not a plus pour mon cher pays.