The idea that there is an ideal place for everyone in capitalism and be able to pay for all the costs of day to day life is some kind of libertarian hacker news delusion.
When they called for research on UBI, everyone focused on what you're focusing on...the hubris that SV thinks it can automate everyone else's jobs. But the point I mention above is, to me, the more powerful one. Freeing people to follow their passions will enable people to give up their 9-5s without first having to save up. Creating a startup is a giant leap into the unknown with only the hope that you'll land safely. UBI is a parachute in case you miss your landing.