I don't know... I know a few people who inherited enough money to be idle and they don't seem particularly happy with their idleness. Could of course be the social pressure we live in, and that could change if we're all idle.
The ability to be at peace
Everyone struggles with it. Would be nice to have some societal hooks so that more people could be confidently serene
And then go about their day
As you mention Lafarge. I think his fallacy and other theorists of its time and school of thinking was mankinds natural sense of enough os enough.
Lafarge wont come true with the quite large inequality of wealth and mankinds appetite for disteactions and general fear of silence and deep contemplation.
In the case of Europe much of generated wealth is wandering abroud (China: goods, US: digital services) so wealth doesn't get enough redistributed but is created somewhere else.
It's conditioning. We cannot be happy idle because society deems idleness as bad. Just like people cannot be happy with a balding hairline because society has deemed it to be ugly. If the trend changes in a century and balding is suddenly hot then the same people would be happy.