Low Birth Rates Are Actually Low Marriage Rates
Low marriage rates exist because everyone wants to enjoy a better life right now, and nobody wants the hassle or burden of tying themselves down.
Women don't want to struggle alongside men; they want to marry someone who already has a house and a car. That's normal—it's the mindset society has programmed into them under a consumer-driven market economy.
Product managers are the ones pushing this narrative: if you can't afford that dress at 20, what does it matter when you can afford it at 40? Your youth is gone. So you'd better hurry up and hold onto it while you still can.
From young men's perspective, they're not willing to spend their time and money supporting someone else's consumption. They want to spend on themselves too—live for today, drink while the wine's good, enjoy themselves first.
On top of that, various media outlets deliberately fan gender antagonism for clicks and traffic, which is why marriage rates are so low.