Labeling one type of morality as the normal, sensible one is cheating, because normality and sensibility are value judgments. You can say it goes against the modal morality. I think that particular one generally gives older people too much of a pass for harms they inflicted while younger, and for which they never made adequate reparations.

If I expand the number of buckets to 100, modeling for 11-year-olds up to 110-year-old and older (but mostly the dead), the responsibility for the debt in 2018 still shakes out to 20% in the 110+ bucket.

We're still paying the debts of dead people. 1846 is the last year in which the national debt could be truly said to belong entirely to the living, and 1974 was the last year we actually paid off any of the debts of the dead, rather than perpetually refinancing them.