There is no proof of social democracy being unpopular in Europe.

The only relevant political movements that advocate against social democracy are mainly extreme right wing. Even those are not growing - and usually collapsing afterwards - because of their individualistic approach to society but because of their appeal to people that feel migration is not good, that climate change doesn’t exist, etc.

Also, every time I read about “social democracy being a Ponzi scheme” along the demographics argument I feel an urge to remember that social democracy isn’t only the pensions system. Healthcare, education, infrastructure aren’t Ponzi schemes neither feasible from a pure individualistic approach.