The gd labor supply will be fine. Where is the wage inflation? There is none at all. Wages flat for 30 years and they are not even keeping up with inflation.
I am pretty sure we can make a society and an economy and a democracy that all works with a steady state population. In fact, I’m willing to bet the future of the USA on it!
The globalists view is that it’s easist, not necessarily better, to just keep growing to infinity.
As to Social Security, we each have our own accounts in the Social Security “lockbox,” don’t we?