Pension expenditure in Spain is out of proportion from any point of view, though. I'll provide links to some graphs because I think they give more information than my words could:

https://elequidistante.github.io/graficos-jongonzlz/pensione...

https://elequidistante.github.io/graficos-jongonzlz/pensione...

https://elequidistante.github.io/graficos-jongonzlz/pensione...

And maybe this is the most illustrative:

https://i.redd.it/uwvgxycxhjeg1.jpeg

So yes, the reason why we are underinvesting in pretty much everything is basically pensions. GDP is up, tax collection is up, debt to GDP is sligthly decreasing... but pension expenses keep growing at a fast pace so there's less and less money for everything else. And I say this with both of my parents earning the maximum pension, so I don't have an axe to grind, but it's just reality.