Yeah, but my point was that our current economic system can’t deal with, not that we can’t deal with it in general. Migrating away from the current system would require the powerful to give up their power, which they won’t do willingly, even as the walls are closing in. (In fact, when it comes to global warming, the walls are closing in).

So, why are declining birth rates not a problem?

It’s not shrinking yet, the birth rate is declining, and the world population is projected to start declining 2050.

Maybe. Could also be that humans never invent anything that comes close to a biological brain. Either because we simply aren’t smart enough, or because civilization regresses before we get there. And there’s several trends going on currently which could cause civilization to regress. For example, climate change and declining birth rates (While we could set up an economic system that can deal with a shrinking and aging population, our current one cannot).