A lot of obviously positive things correlated with lower birth rates, like not having half your kids die before they reach adulthood, being able to treat infections with antibiotics, not needing a crazy amount of labor to keep subsistence farming going.

Birth rate collapse itself is a positive thing, this planet can’t ecologically sustain pre-industrialization birthrates combined with modern medicine and life expectancy. Back in the mid-century there was a lot of academic concern about overpopulation.