Social security/pensions can be designed in several ways. America, and Belgium, for example, have chosen a system where the current workers pay for the current retired, and the future workers will pay for the future retired. This works great as long as you assume an ever-growing labor pool. In the current boomers-retiring along with higher life expectancy climate, such a system is a travesty, with ever-less working people supporting ever-more retirees.
Obviously, this was known well back into the '90s. And just as obviously, measures taken to alleviate this - setting money aside for future retirement payments and all that - has been turning out to be completely empty boxes, or IOUs with nothing supporting them, or has straight-up been gutted or stopped for short-term savings.
Some countries have opted for a system where each worker pays for their own pension - just like in private pension systems. Of course, this means those who work will have a decent pension...But house mothers, disabled people, and what-have-you who haven't worked a full career for whatever reason, are left in squalor.
Some countries, like the Netherlands or Norway, have built a system where every generation is building towards their own retirement as a whole - a bit of a mix of the above. Technically superior, but such a system requires a LOT of upfront money and investment, which not every country could do - both of the countries named used billions of oil money to set their systems up after WWII.
When the Belgian SS was designed after WWII, one retiree was supported by 16 workers. Now, one retiree is supported by 4 or 5 workers, and it's expected to drop down to about 2.5-3 before the boomers start dying off. And despite what some people have already been claiming, Corona won't really make a dent.