Low birth rates are associated - under societies that actually care about raising their children and provide them with education and good living conditions - with economic and social factors. If you, as a parent, are able to provide for your kids and feel comfortable with the support network around you - schools, family, etc, you feel more comfortable raising a family and extending it. This also promotes one being raised with values that promote caring about others.
What we see In western societies nowadays, is something completely different: people feel hopeless and exhausted -due to ever declining economic conditions- and give zero fucks for anyone but them. It's the "me, me, me, and now!" society that has been (and continues to be) promoted to us. This lead to the loss of many values that are family oriented. Women are whores, men are weak incels, LGBTQIAZZZZ+-/√ etc. - whatever floats your boat -, but you get the picture.
I don't want to go full sperg on this, but in case you're wondering where this is coming from, you should definitely check Marx's ( and associated Frankfurt School, Fabians, etc) view of the family: he saw it as key to passing the social, cultural, and religious ideals of the established order on to the next generation. Families tend to curb antisocial behavior and block radical changes. Marx saw the family as the means by which the establishment defended what he called"outmoded" and "oppressive" ideas.
Western societies were based on family and values. Strong families are the base of societies since the human race started to evolve and settle. Strong families are likely to stand up, provide support for each other, and reject oppression from the state. But western civilizations were built on a social contract for the late centuries: you work and pay taxes so that, in the future, you can enjoy retirement and a pension being paid for others repeating the cycle. This cycle is broken. For many countries, it's nothing but a pyramid scheme, supported only by governments (private bankers, actually...) printing money out of thin air. Everyone knows it, but no one is willing to admit it.
How do you make everything even worse - I'm thinking about "we the people", not the elites in charge- ? Promote the most degenerate shit possible, validate "me" as the center of everything, destroy families, and import a bunch of people that are way easier to control and don't hold the same values as the society they're intended to replace.