We would spend our time, doing art, music, entertainment, or any other leisure related activity/job
And who's gonna be paying you to spend your time doing art, music entertainment, or any other leisure activity?
That seems to be the mistake all the pie-in-the-sky thinkers make; they just assume that, with the elimination of work for humans, the elimination of a weighted financial system designed to separate us into differing economic classes will disappear with a magical POOF.
It's not even that. As people become more productive, that increase in production leads to better and better products. Those products require more labor to afford. The general population will never have that much leisure time because there will always be more expensive items to buy due to that increase in productivity. Sure, I could cut my work to 4-8 hours a week currently and live like what was considered a 'good life' around the end of the 19th century. I know some people who have or do live like that. Backwoods guys that live in a 10'x10' shack and satisfied to make enough to buy the food, clothing, and books. People that dropped out of their PhD programs to live the life of a beach bum. Idealistic gypsy wanderers that essentially couch surf across the world writing books on their hand me down laptop. Trouble is I want lots of things they didn't have then like cars, computers, cell phones, internet connection, decent sized house full of stuff, etc. That requires me to work at todays levels enough to get those products.
Which is why those jobs that went to China will not return. They are still worth what the Chinese are getting paid for doing them. Nobody wants to work that much to receive the level of compensation that they would receive. If those jobs come back, they will be automated and the automation will be handled by a relatively few skilled workers. The world may always need ditch diggers, but 50 guys with shoves that have to be supervised to make sure they are doing a good job aren't worth one halfway competent guy with a high school diploma (and probably more these days) who can run a $100k ditch digging machine safely.