It’s not possible for everyone to have decent living standards. China and India need to decrease their birth rate so the rest of the world can thrive
https://www.macrotrends.net/global-metrics/countries/ind/ind... https://www.macrotrends.net/global-metrics/countries/ind/chi...
It's not self-evident that life is such a zero-sum game that more people necessarily means fewer resources to go around; I'd even venture that the last hundred years of development suggests the opposite.
It's quite possible that more people enables a slew of network effects (such as technology improvements due to more minds attacking a problem, say) that improves everyone's living standards.