You are so right, data wise, it's a demographic time bomb... The ratio of working to non working is critical, and has completely changed since the European welfare states were established. Dont know euro data, but for the UK there were about 6 workers for every 2 retired back in the 1940's when the State Pension was set up. So it was affordable, and the deal was you pay for people currently retired; in return when you retire someone else pays for you. Pretty much the definition of a ponzi scheme (!) but the demographics worked; and following the brutality of WW2, people rightly wanted a better future. Now it's 2 workers per retiree. Falling birth rates and increased longevity mean the sums just dont add up anymore.
... But I dont see an answer. Welfare is a clever Social Democratic trap. It's unaffordable but cut back the welfare state and plunge people into poverty? No thanks for most people, and we already have record homelessness etc... Plus no one would get elected on that basis. So, like gov debt, the can will keep getting kicked down the road I guess... Europe (the continent) continues to stagnate...