I reckon just about everything has changed....
The typical job was a real job, where a real man stood up for about 10 hours a day, usually in a factory or on a farm, doing heavy physical work. Hot steamy factories or baking hot open fields were the order of the day. Lotsa grease, lotsa flies, plenty of dangerous big equipment flying around at high speed. You had to actually concentrate on the job. No earphones, no texting, no "let's just nip down for a short black", no OH&S, no lawyers to bleat to.
Starting that type of activity at 15 and constantly working for the boss for 50 years, most people were lucky to retire at 65. Most had either dropped off the perch by them, a few had even been injured / killed by the activity. Pensions weren't really a big deal, and very much earnt if you made it through.
I remember reading that in the 50's or 60's, men's life expectancy was about 68, so the lucky ones who got thru only drew a pension on average for 3 years.
Contrast that with today, where "men" typically stay at Mummy and Daddy's hotel until they are at least 25 or 26.....usually after they've graduated with their 3rd degree.
They then get employed to sit in a female friendly, non-confrontational, completely sterile, ergonomically designed safety zone on level 42 where they sit in front of a "haunted fish tank" that is strategically positioned so that no-one can see what they are looking at, and surf the web, staring into the fish tank whenever their boss - Yvonne - doesn't slink by in her pencil skirt and high heels.
They read about all these miracle investors who retired at 32 and think to themselves "too right, I've been here 2 years, 4 more to go and I can retire as well."
Four more years roll by and they're adamant "damn straight, I've really put out staring into this thing and typing furiously....my fingers are frazzled.....it's time for me to retire". He's probably got 60 years in that zone to go.
I can't possibly see why anyone would think that our current mode isn't sustainable.