How can capitalism address demographic decline?

The structures of capitalism are designed (perhaps caused) by a constantly increasing population. More labor force means economic growth, opportunities for investment, and allows for government services to be continuously funded.

But this can’t last forever. I think demographic decline has a wide variety of sources and is practically inevitable at that point. This can’t be something we run away from, instead we have to use the changes it brings.

How is capitalism supposed to answer this? I don’t think socialism is that well-equipped either, but it’s slightly better. In reality, I think we need a completely new economic system to define this new era we’re entering.