As someone who is always doing side projects or at least thinking about them I do wonder if for certain part of the population having more free time would also mean more creativity and a net improvement for all of society. I know I'm biased and it's wishful thinking but it could be true.

You nailed. True, less work means more time for side gigs, ideas and self-improvement, you are not the only one that hopes for a future like this. Every day more I think Star-Trek predicted the future with a degree of precision quite impressive.

This is the basis for Marx' infamous "hunter, fisherman, herdsman or critic" quote from The German Ideology - the notion that wage work alienates people from the work they do and end up controlling them.

I wasn't familiar with the quote:

“For as soon as the distribution of labour comes into being, each man has a particular, exclusive sphere of activity, which is forced upon him and from which he cannot escape.

He is a hunter, a fisherman, a herdsman, or a critical critic, and must remain so if he does not want to lose his means of livelihood; while in communist society, where nobody has one exclusive sphere of activity but each can become accomplished in any branch he wishes, society regulates the general production and thus makes it possible for me to do one thing today and another tomorrow, to hunt in the morning, fish in the afternoon, rear cattle in the evening, criticise after dinner, just as I have a mind, without ever becoming hunter, fisherman, herdsman or critic.”

Now that we are quoting, of course:

"A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyse a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects."

-- Robert Heinlein

> It may seem strange to think of a nurse or driver being more useful when contributing 30 hours a week instead of 40, but that’s because we don’t appreciate the potential range of their decision making quality, error rate, and so on.

Improved decision making quality or not, wards with a nurse on call still need 20% more nurses. And there's absolutely no way a driver is delivering 20% more stuff in four 8 hour days to make up for being absent for the fifth. And most of the "place needs a person to be on call for this shift" type jobs are the hardest to automate

Right, this would be a preference change for nurses whose attention is more valuable and who don’t burn out (decrease quality of care over time.) Same for more attentive drivers. This is consistent with how the perspective changed of jobs we consider compatible with shorter workweeks.

In addition to automation for jobs where attention and reason doesn’t contribute to success (which is how you’re describing nursing and driving; I of course disagree), there will still be a market for hourly pay and people who really enjoy and are suited to overtime, as well as other factors. The transition is complex.

It's not about "where attention and reason doesn't contribute to success", it's about the simple reality that if someone commits to having something staffed "5 days a week" or "24/7", then either their costs have risen 20% or the salaries have to fall 20% when the working shifts fall by 20%. That might be acceptable to some business and staff (part time employment is already a thing) but magical productivity improvements aren't always as achievable as certain knowledge work fields. More attentive drivers don't go 20% faster or have 20% more space in their lorries, and for that matter I'm extremely sceptical people would pay 20% more attention to the roads working a four day week than a five day one.

Well, you are right that if we continue to want butts-in-seats commitments without thinking about what we are looking to get from them, then nothing will change.