Old age learns about less after a lifetime of more.
How science dwindles, and how volumes swell, How commentators each dark passage shun, And hold their farthing candle to the sun!
The ordinary American - as far as I can tell - knows so much less than he did fifty years ago and has such poor work habits compared with fifty years ago that the average multiplicand of knowledge/capabilities is a much smaller number than it was in 1961.
... life is broken down into these stages: you're born and you don't know how anything works; gradually you find out how everything works; technology evolves and slowly there are a few things you can't work; at the end, you don't know how anything works.
I wish I knew as much about anything today as I knew about everything when I was twenty.
In the case of various kinds of knowledge, we find that what in former days occupied the energies of men of mature mental ability sinks to the level of information, exercises, and even pastimes for children; and in this educational progress we can see the history of the world's culture delineated in faint outline.
The age was still dark and reeked of the havoc and misfortunes of the Goths who had put all good literature to destruction. But, by God's goodness, in my time light and dignity were returned to letters, and I see there such improvement that today I would have great difficulty being admitted to the most elementary classes--I, who in my time was reputed to be (and not wrongly) to be the most knowledgeable person of the century.
The fractious, know-nothing thirty-year-old is what we got when we let the twelve-year-old drop his books and take up the screen.
The Dumbest Generation: How the Digital Age Stupefies Young Americans and Jeopardizes Our Future
It was too difficult. People weren't prepared to put in the hours on the donkey work - you know, dates and facts and so on. I think in retrospect my generation will be seen as a turning point. From now on there'll be a net loss of knowledge in Europe. The difference between a peasant community in fourteenth-century Iran and modern London, though, is that if with their meager resources the villagers occasionally slipped backward, it was not for lack of trying. But with us, here in England, it was a positive choice. We chose to know less.