I’m not sure everybody in the world would agree its not over populated but underpopulated. We cannot or choose not to feed, clothe, house, educate, employ, and treat a significant number of them, so I would question that we should be breeding like rabbits to use up more of our diminishing resources.
I’m not sure I ever really understood this Catholic directive to give birth often. Most of the large Catholic families I knew from my childhood were not so very happy. The financial burden was miserable, none of their kids could go to college, and NONE of the kids ever had more than one or two themselves. They didn’t find it such a happy childhood.
I also am not clear about the argument that if God wants it differently, he’d change it. There is the well worn story told in a variety of ways, wherein the moral of the story is…God expects you to do you part too. To dirty up his world seems pretty rude on our part.