If you could alter human nature so that everybody trusted everybody else, and everybody cooperated with everyone else, then people could work significantly less.

In that scenario you wouldn't need police, courts, food inspectors, restaurant inspectors, auditors, or a military because everyone would just be cooperating and honest. Offices would need far fewer managers because managers would just be coordinating work, and never have to worry about employees slacking off. HR would never have to fire anybody or discipline them because everyone would be trustworthy. You'd need far fewer executives, and the executives would be honest about how little they worked, and wouldn't ask for absurd compensation.

But, that isn't humanity. Throughout history people solving disputes non-violently has been extremely rare. It's possible among small isolated groups who all know each-other, but as soon as you get towns, people are no longer able to completely trust the people they encounter day to day.

People are also underestimating how good we in the developed world have it today. Working only 40 hours a week was something only the privileged few used to be able to do. Being able to choose what you want to eat is something that only the nobility used to do. Could it be better? Sure. Has it gotten worse on the small time scale of decades? Maybe for some groups. But, for most of the world the last few decades have been ones where the standard of living has gone up by leaps and bounds.

Yes, we should guillotine all the rich, but look at the immediate aftermath of the French Revolution to see how a fully justified plan can still cause death, starvation and chaos in the short term. Humans are still animals, and although we can sometimes recognize there's a problem, cleanly transitioning to a better system without chaos and death is not something we've figured out how to do.