If you have a shrinking population then the % of the population that makes stuff gets a lot smaller so everyone has to be poorer. No "economic system" can change that.
sure, but if people are too exhausted to make the time to have a family (a.k.a nookie) then its maybe worth examining [0] if "constant growth" is societally sustainable
[0] https://www.theatlantic.com/business/archive/2017/07/japan-m...