People read that and it registers as infants dying within days after birth. But life expectancy for 10-year-olds has doubled: https://ourworldindata.org/life-expectancy. I doubt that your comment makes people think of dead teenagers, even though your post doesn't contradict that interpretation.
Even for the 40-year-olds, life expectancy increasing from 68 to 82 years means a >50% increase in "time remaining" which isn't something to sneeze (cough?) at, although I have to reluctantly acknowledge that I remembered it being even larger than that.
Look at the England a whales data in your link, in 1841 10 year olds could expect to see 57.6, or another 47.6 years. In 2013 that bumped to 82.2 or another 72.2 years. By 20, they could likely hit 60 or another 40 years worth of life, and by 40 they where up into ~67.4.
However again the difference is largely one of lack of war and famine rather than medicine. The chart is bouncing around because of events that killed large numbers of people, but it smooths out as you approach today.
PS: Their Spanish Flu suggestion is off, it was actually WWI and the flu that’s responsible for much of that drop as seen by 40 year olds being largely unaffected. https://en.wikipedia.org/wiki/Spanish_flu#/media/File:W_curv...
I chose 40 because it wasn’t medicine that made the biggest difference for 20 to 40 year olds but war. And actuarial tables can’t predict wars only account for past wars which make current estimates misleading. Aka we don’t have a lifetime of data for people born after 1920 only estimates.