Your response is kind of frustrating because I feel we're on the same side of this, but you're just not getting it. It's like you have a knee-jerk reaction about what a job is, and there's a blindspot where you don't envision what it
could be.
When a plumber gets satisfaction from a good day's work of fixing piping in people's houses, do they get their purpose in life / sense of being needed and useful (note: not the same thing!) from an authority figure? Hell no, unless you think clients are authority figures.
But they are getting this sense from their work.
Heck, even in standard office jobs, I doubt that too many people get their sense of being needed and useful from their bosses or other authority figures (if they get it at all - you don't have to tell me about bullshit jobs). They get this sense from coworkers, clients, or other aspects of the work itself. That's certainly my personal experience. We're social beings, not obedient worker drones.
And I don't know how to put that in a way that gets the point across, but I think a lot of techy types are actually quite arrogant and selfish when they dismiss full employment and think that a UBI would solve all problems.
I get it, most of us would happily work on random open source projects or whatever if we had sufficient UBI, and a lot of that work would be useful to many people. But we should be aware of how rare that is and how lucky that makes us.
Most people don't have that drive or that opportunity, but would still benefit from a social framework in which they are nudged towards doing useful things that they can take pride in and get rewards for (both monetary and psychological). It's like going to the gym: most people don't have the drive, but would ultimately benefit from the offer and a bit of nudging.
Full employment can offer such a social framework (if done right, of course), while a UBI can't (no matter how it is implemented). Who are you to deny this to other people just because they're different from you?