This is the real problem. While it may be good ecologically for population growth to slow and then reverse, it will lead to what I've long called "planet Japan."
If you adjust GDP for population growth Japan is actually doing quite well. The fact that it has a growing economy and a shrinking population shows that productivity is going up. Countries like the US have historically had high population growth which is reflected in higher GDP growth.
No issue there. The problem is that this completely breaks all modern finance, which is built on the assumption of permanent macroeconomic growth to deliver returns and permanent inflation to continuously re-price debt.
