So folks work at McD's and the feds pretend its 'employment' but nothing like they used to earn.
Economics isn't solved with platitudes. We're in the middle of a major disruption and it isn't going to be pretty.
My hint at the trades (HVAC/Plumbing/whatever) was that the supply will be incredibly low in the next decade or so, when many of these workers retire, but their demand will be higher than ever.
Printing money without adding wealth means each unit of currency is worth less, which tends to ruin the whole "free money" thing.
We print money now; but its loaned out thru the federal reserve. How is that ok, but not directly distributing it to citizens?
Economics is complicated. A UBI can work.
If you ignore money and look at the flow of stuff, there's nothing impossible - we produced enough to feed, clothe and house all those people back when they worked, and we would still produce enough to feed clothe and house all those people even if half of them have no need to work.
It's a distribution issue. And really, if/when technology causes significant permanent unemployability, there are only two options - either the society chooses to simply redistribute that stuff to people who don't work (despite, as you say "it simply isn't fair to take from those who sacrificed their time and efforts to build wealth"), or the society chooses not to do so, in which case they don't get fed, clothed and housed, and die.
There's no third option - they can't not be a drain on society (that's what being permanently unemployable due to tech changes means) while they're living and need resources. Either society provides basic income also to those who aren't sufficiently productive to earn a living, or they will try to take those resources from society (theft, crime, revolution), or they'll die trying. Thankfully mass technological unemployment isn't that close yet, so we have time to fix the social issues, but it's coming.