The only way to fix this "demographic problem" is to let nature run its course.
“No surprise here. The idea that everyone in a country can retire and live 25+ years without doing any productive work is delusional.”
You should learn some math. Einstein said compound interest was the greatest invention in human history. The proper amount from each paycheck, invested well over 25 years, is fine to ensure the continuation of that level of life. Of course when the government owes 20 Trillion the Fed keeps rates near zero and that no longer works. But in a normal economy, a smart person can indeed work 25 years and continue life as normal.
Then they can do many other things in life.