>> Since when is it our responsibility as Jews to solve world problems?
Since Avraham opened his hotel?
Main reason for improved childhood survival is due to vaccinations and improvement of public health, such as milk Pasteurization lead in US by Mr Nathan Strauss from Lakewood 100+ years ago. (this partially reversed problems created by industrialization). Also, science advances primarily by another German Jew – Fritz Haber, who got Nobel for saving billions of people from starvation and allowed billions to be born but was written off history for also developing poison gas that killed thousands. Thanks to these scientists and public health experts, we had unprecedented growth of humanity in last 250 years …
another aspect of current changes – it used to be that rich, educated, and successful people had larger families, and less well-to-do did not. Most of us are probably coming from those rich people. Now, richer and educated people have less children, and less educated are moving into depopulated countries. It is an open question what will happen going forward with this …