I used to be pretty big on the UBI bandwagon but I've come back to Earth recently and the reason is pretty simple - while we
certainly do not take advantage of the total sum of intellectual talent available today - we squander a huge amount of it to poverty and cultural isolation - even with global UBI and universal access to education there will
never be a population where even the
majority of people can do those jobs.
Tech is a bubble, and we dig ourselves in deep. But you don't need to go to the third world to find illiteracy and ignorance. You often don't need to go more than a few miles in any given direction to find entire populations of doomed people - they have no ambition, education, and most importantly no desire to ever have them. The smart ones leave, go to the big city, succeed in school and go to university and end up successful, but for every capable intellect there is often someone who just can't. Its no different than introversion vs extroversion - some people crave the new and different and some people crave consistency and pattern.
And we might like to think otherwise, but automation replaces the routine, not necessarily the physical. But a lot of people don't have the capacity for boundless creativity, in my experience it actually hurts some people to have to think outside the box that much. Like headache causing stress and frustration. They don't become scientists not because the opportunity is not available to them fiscally, but because they cannot think like that. At least not in a professional capacity with forty hours a week consistency.
I don't think we can eliminate that factor. And I think it is much larger than anyone who promotes UBI as leading to an era of scholars and scientists aplenty gives it credence for. Or for not recognizing that as a species we are barely evolved beyond animals that could only, at most, do simple tool manipulation and use. Who couldn't understand the concept of self. Asking for human brains to on average be innovative, imaginative, and capable of running in the highest states of consciousness we can reach on a near constant basis is asking too much of a lot of people.
It asks too much of me many days where I try to find something rote to do rather than face new problems that can get overwhelming, so from someone not on top of the brain potential spectrum, there is a reason why predatory repetitious skinner boxes work, why addiction is such a big problem, why people get stuck in their ways and why change is hard, and these aren't things we will ever eliminate from the species entirely without a serious investment in transhumanist innovation. These people will not become scholars, creatives, or thinkers.
That being said, I'm not convinced its even a problem. A lot of why people crave "meaning" in their lives is the fear of loss. Having a purpose gives you an anchor to always ensure you never go completely adrift from your life as it is. You can lose your job, home, etc but if you have a purpose and feel like you can do something it gives you the strength to keep fighting to survive.
With a UBI, the fight to survival pushed on pretty much everyone by capitalist economics as a means to spur growth changes fundamentally. I would be interested how societies pressure to have purpose and how we build our self worth would change with it.