And I would disagree with the "exclusively" part of that sentence. I've already shown you how millennials benefit from Obamacare. Your note about young people subsidizing over-60s is a red herring. Over-65s are already on Medicare and it's pretty good. Why wouldn't millennials want that for themselves?
Most people don't understand taxes and money - this isn't specific to any particular age group. And frankly, as I've opined elsewhere on this site, retirement savings laws particularly are overly complicated for nearly everyone.