Great, how do we do that without reducing output? If the share of society that supports all of it cuts their hours in half, their personal situation will certainly improve. But a lot of people will go hungry.
If everyone cut their hours in half the only thing that would happen is growth would slow a little bit and billionaires would make a little less money. If people are going hungry, that's not a problem of productivity. There is more than enough money in most Western countries to make sure that doesn't happen. The only problem is how that money is distributed.
I'm not talking about distribution of profits, I'm talking about raw output.
Sure. But not everyone wants the same, and central planning has proven that it's even more inefficient and wasteful than the capitalist free market system with its insane shoe-storage-system-stores and shoe-storage-systems-insurance-salespeople.
You don't need to play the game, but being inside the game also provides security. Humans are very social, the odd outlier that prefers his own company and is happy to trade comfort and safety for simplicity and freedom really is an exception.
What we have got though is an onslaught of marketing encouraging us to thing of a vehicle as part of our identity and status. New tail fins making us think our current model is obsolete. Advertising implying that we aren't a good parent if we don't have a new German car. Product placement telling us suave British spies all drive Aston Martins.
The car market is the furthest thing from utility.
Will they? Honest question. How much of the labor share is human versus automation in 2020?
The real issues with scalability are things like medical care and other higher skilled labor - not just because of task switching inefficiencies but because any proportional hour reduction means increased demand - assuming that the hours worked are useful.
Less skilled labor is more or less commoditized and would be easier to spread the burden around and would likely show a boost instead of a decline in productivity (although involving say 10 people working 4 hour shifts instead of 5 working 8 hour shifts).
Regardless of stance on what we should do a massive societal lifestyle shift would neither be easy nor well received.
Consider the fashion industry, to take a somewhat arbitrary example. I don't mean the clothing industry -- most of us would agree we need clothing -- but the fashion industry, which exists not to clothe us but to convince us to constantly buy new and different clothing, because otherwise we won't be seen as "cool" or "fashionable" or "successful" enough.
And it's not the only such case.
Also there is the whole essential vs non-essential work debate.
Don't think it's such a black and white picture, there are many variables to consider, probably way too many for a human brain to comprehend.