Edit: meant to say below replacement birthrates

In the grand scheme of things, everything about our lifestyles in first world countries is unsustainable, including reproduction.

If you had a country the size of the US population all living modern lives, using dating apps, waiting until their 30s to settle, you'd see the population dip below 30 million (roughly the size of Nepal) within 5 generations.

You might say modern dating is essentially the equivalent of an evolutionary dead-end or a species death dance. But how long is this sustainable for? Is there going to be an inflection at some point where we revert back to more traditional dating and marriage practices? Or is it just our fate to be eventually replaced by Mormons and Hasidic Jews?