The "system" would fall apart if people didn't work for at least half their lives, true, but it is absolutely not true that we need people to work until they're 70.
Let's say you live to 80, half your life is 40 years. You only start working a decent job around ~22 years (4 year college degree).
22+40 = 62, pretty close to 70 already. Assuming some people die early, so others have to pick up the slack, some people work part time, etc. and you end up pretty damn close to 70.
https://www.latimes.com/california/story/2022-03-13/lopez-co...
https://www.foxnews.com/health/100-year-old-surgeon-wwii-vet...
https://www.rferl.org/a/my-hands-don-t-shake-says-world-s-ol...
https://www.boredpanda.com/89-year-old-surgeon-alla-ilyinich...
I am wondering why aren’t you on this list… Look at all these billionaires, since we have some I assume you are on as well?
Seriously, there's 800,000,000 people over 65 on the planet[1], and you're judging all of their abilities based on a two digit number, instead of individually on their actual health and abilities. That's ageism. That's a yesteryear worldview that people have been fighting against for a long time.
And that "I thought I could say horrible things and nobody would object" is common red flag behaviour mentioned on all the "what's a red flag about X" threads that appear on Reddit constantly; "my boss said something rude about <group> and nobody said anything". That you didn't expect an uproar about judging people you don't know as incompetent or incapable based only on their age - and got an uproar - should be a reason for you to reflect.
[0] https://www.youtube.com/watch?v=pCXBPLl7gXc
[1] https://ourworldindata.org/grapher/population-by-age-group
“lets get them all to a construction site” - this is not my position.
It’s not that your (implied, guessed-at-by-me) idea is wrong on its face. It’s that you choose to (1) imply it, (2) in a snarky way that is insulting (even if true), and then when someone claimed a counter-example, you immediately fell back on made-up numbers for why you wouldn’t have to display the slightest curiosity as to how this supposed impossibility came to be.
You assume they’re lying? Why should anyone think better of you? Anyone can lie on the internet.