Unless your nation is self sufficient, there are always costs to capital controls. The choice is not let everyone live happily ever after and restrict trade. Tradeoffs are made to remain competitive on a global playing field.
If China and other countries are bringing 1B+ people online to make products at a fifth of your wages, then it is only a matter of time before the buyers outside the country start buying from them.
What happened was that American (and European) corporations started producing their goods in other countries, because it was cheaper for them.
Like, I would have no issue with this in general if China developed their own companies, rather than already profitable US companies slashing their labour costs massively by using cheaper labour. It's super problematic, and while one can argue it's been good for the world, it's been pretty crap for all the manual/manufacturing workers in the US, Uk and other developed countries.
Full disclosure: I'm from Ireland, and this sort of outsourcing was what employed my Dad (and now me).
If China and other countries are bringing 1B+ people online to make products at a fifth of your wages, then it is only a matter of time before the buyers outside the country start buying from them.