In Europe 10+ children was quite common. So there was certainly at least as much, if not more, population growth. And as others pointed out, there was an age gap there too, as it wasn’t uncommon for notably older bochurim (or even widowers) to marry considerably younger brides. So the question still remains, what’s new in the 21st century that makes this a new problem? The suggestion that the problem was simply ignored (or oblivious) for hundreds of years, and simply allowed to fester, doesn’t shtim.
Lower childbearing mortality. I do admit that if 2% (just making up a number) of women die in childbirth, then the crisis would not exist (as is now).