The solution involves restoring and teaching a Judeo-Christian worldview and fencing out the toxic humanist worldview that is now setting the stage (if Christ does not return) for a civilization-ending population collapse akin to the dark ages that ended the Roman Empire. Back then the western Empire saw cities become ghost towns with only 5-10% of their peak population, even before the barbarian invaders hit. The invaders were pushing in on an undefended door to an empty house.
I am convinced that Christian values are essential…but I am not convinced that fertility issues will be solved by solely Christian values. I think that unique government structures and solutions will be shown to work in some smaller nations…these successful techniques will then spread as other nations see their success.