That’s true, but it supports my point not yours. In 1950, Pakistan and China both had a GDP per capita around $600. Today, China is probably within a generation of becoming a developed country and eliminating child labor. Pakistan is nowhere close.
Of course capitalism doesn’t eliminate child labor overnight. Villages in Pakistan and to a lesser extent China would starve to death if you eliminated child labor overnight. But capitalism is the only system that has proven capable of nearly eliminating it from a society over time.