This is a shrill take in the same platitudinal vein as saying there should be world peace by now. You're regurgitating techno-optimist fantasies you've read from someone else and have come to mistake them for reality or desirability.
The median individual is not going to be working less than 40 hours a week. The system has found a balancing point and people will compete with each other for the money, resources and status as much as their sanity can endure it. There is nothing anachronistic about it, because it has been the case long before 19th century and will remain the case long after 19th century.
In a world of structural demographic compression and labor shortages popping up, I'm unsure if this assertion is accurate. As labor supply contracts while demand remains constant (or increases, due to aging non prime workers who consume without producing), labor leverage to move to a 4 day week increases.
Today, ~1600 school districts across 24 states in the US are on 4 day weeks to attempt to retain teachers, for example.
We are in the computing era (plus robotics), not in the 19th century.