Keynes conjectured reduced workload (or the equivalent: ever rising compensation) would be the natural consequence of increased productivity. What went wrong seems to come from at least two things he did not expect.

Firstly, rather than continuing the trend of increasing political power in the early post war period, the productive classes, including employees, have lost political power relative to the ownership classes and thus control of resource allocation decisions.

Secondly, outside tech and a few other vibrant sectors, capital sits idles or is used unproductively (for example in real-estate speculation) or even to destroy wealth (for example through expanded rent seeking). This is relevant because in these cases the increased wealth from increased productivity is just wasted rather than being used productively or at least spent on quality of life.

It's nice to see that somewhere, a few people are trying to address that first issue.