In real terms the budget is the largest it's ever been, it's a relic of the time when people worked and died shortly (a decade) after retiring, not when they live for 30+ years longer.
Which it needs to be given the demographic changes you note. It's about 15% smaller per capita than comparable countries spend. That would suggest that we need to increase the budget if we want comparable service.
To bring it to a comparable level to similarly wealthy countries would take an increase in funding of 20%-30%.
https://data.worldbank.org/indicator/SH.XPD.CHEX.PC.CD?locat... https://data.worldbank.org/indicator/SH.XPD.CHEX.GD.ZS?end=2...