My biggest criticism is the lack of acknowledgement of HOW the work week was reduced. Maybe you addressed this in the end, I didn't finish all of the article. But, we literally had armed militant workers fighting for these things.
We also has a work force of mostly men subjugated by capital; and woman as house slaves subjugated by patriarchy.
As the ruling class attempts to erode the progress of the working class; I don't think it is helpful to hold onto to a narrative of "it was worse back then" to attempt to normalize it being "better" as material conditions decline again today.
Workers, civil rights activist, and feminist resisted and bled for the progress that was made. If we don't continue to resist and fight for what they did we do not respect them. It is not meaningful to look at the past and be satisfied with the progress that those that fought for it were not done fighting for.
Do we think MLK was satisfied with social progress when he was shot in cold blood? History classes definitely want us to think so.
The major flaw in the article is
the distance between today and 2100 will be at least as large
And shows a misunderstanding of history and a bias towards the narratives of how capitalism is a beacon for "progress". It is not. And the world we see today is repeating itself.
The current historical analysis points to a major lack in the story. That between 1900 and 2000 there were multiple world wars that look the lives of millions and millions.
As someone living in that period now. I think learning how to avoid mass suffering is far more important than some spreadsheet that tells me anyhow productive we've become.
Edit: I read to the end. You did address some of what I said. But you should really open with "it was fought for by people that refused the 60 hour work week" and not wait for deep in the article for a fundamental part. I'll leave my comment because its still ok for discussion. But I think we probably agree more than I initially read from.