Children aren't being produced. Birth rates are declining.
People conflate the carrying capacity of the economy with GDP, but these are different. The economy grows but requires fewer workers over time. As the carrying capacity decreases, the population decreases. On the ground, this manifests as the inability to afford child rearing.
The excerpt you cited assumes that this race of workers must afford to perpetuate itself in order to be viable. It cannot perpetuate itself, and it is not viable.