The theory is sound.
You'd have to work over 50000 years at making 1 million dollars a year with no taxes to even come close to catching up to the wealth in being the top 100 richest in america
That's dynastic wealth and there have been many many many studies/research into why dynastic wealth doesn't allow for a "lower barrier of entry" as you're suggesting Bill.
Even Adam Smith writes about rent seeking and how the wealthy will start going towards such practices to maintain their wealth by working as little as possible. It's why he wrote a second book about Morals of wealth.
But more importantly, one should appropriately ask, are we working towards the betterment of society, or are we simply working because it's something to keep people busy or are we working because we have been enslaved to a particular system where if we want to survive, we have to work due to policies of a small group of people.
Keynes talks about how it would ahve been great if full automation happens and that if we only had to work 10% of the day and still offer the same productivity, people will live more fruitful and happier lives.
There's obviously alot of economic schools of thought and plenty of well written ideas around the subject, as such my opinion is that UBI is a good thing. I'd much rather those who can't, go back to school to learn, than work dead end jobs then to simply ask the government to pay those dead end jobs more money. I'm not a believer when folks say "Janitor is a noble profession". Working hard to move forward in society and improve society is a noble profession. Working hard becuase you want your kids to be smarter and not be a janitor is a noble profession. Being stuck at being a janitor for no other reason except you want to be a janitor is not noble. People seem to conflate many of those ideas and boil it down to 1 step talking points, which this shouldn't be. The UBI in my opinion is the first step in allowing those who are forced to be Janitors, (language barriers, skill barriers, etc) go back to school without having to worry about certain survival basics that shouldnt really occur in one of the richest countries in the world. What's the point of being an American citizen, if the American government won't take care of you? (The low taxes might be valid though hah)
My way of paying for it though, would be a wealth tax on those who hoard wealth at the very top. If you flattened out the wealth inequality to say that the top 3 men of America doesn't own more than 50% of all wealth in this country, you could pay for UBI and move to a flat tax that people like to talk about. I would decimate dynastic wealth in this country. You want to be super wealthy? You work much harder for it. For everyone else, it should be, work hard, retire easily without having to find another job just to support yourself.