I don't think anyone is proposing that humans then do nothing and watch VR porn while being tube fed for the rest of their lives. There is indeed an infinite amount of things left to do.
The question is given this 'initial condition' where everyone is where they are currently in 2019, who does that work.
Is it the 56 year old truck driver who's now 100k in the hole for the truck he bought that's now useless with automated trucks and who's using his disability benefits to feed his opiate problems from the painkillers he needed for his back from all the hours in the truck? If he's not the guy we're putting in CERN trying to demonstrate the next Higgs field interaction, what do we do with him?
but to follow your line of reasoning, what you do is walk up to him and say, "hey, in the next 10 years, your job is going to be automated. every year, your chances of losing your job goes up. what do you want to do? [...listens...] ok, let's set up a transition plan and make sure you're ready when the time comes." and who knows, maybe he's a hobby machinist, and can work for CERN custom-building the crazy one-off contraptions they need.
it's paternalistic and patronizing to make assumptions about the abilities and motivations of millions of people and 'solve' their problem for them. it's how we get misguided social programs that waste billions of dollars (i'm not against social programs, just misguided ones, and they're really, really tricky to structure properly).
Our mental plasticity just has age related limits.
I'd also debate the conclusion you're making on which approach is more patronizing. I'd assume giving you (and everyone) the means to make your own choices with money is less patronizing than appointing your specific job as a lost cause and appointing new jobs for you to go train yourself for.
also, on people's intrinsic motivations: people don't want money in and of itself. people want esteem (e.g., status) and influence (e.g., power). jobs and careers provide those things; handouts do not.