Sacrificing children was just another way to get rid of excess population and would absolutely improve the lives of whoever was left.

Any children not sacrificed would have to die by disease, war, or starvation at some point anyway, because again, the population cannot grow above the Malthusian limit.

This core concept - that preindustrial people all lived at their Malthusian population limit - is incredibly important in understanding the preindustrial world and it's shocking that it's not more broadly understood and applied.