Automation that makes 50% of people worthless means that the remaining 50% of required labor can produce the same amount of goods and services.
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.
But it is. The folks who used to be machinists or warehouse workers or assembly line employees, are now working McD's or worse. It looks like employment but in fact the total value of US employment is dropping like a stone. The stats just say "92% employment" and we say "Yay! That's good" but its not good if most of the new employment is a drop in pay and standard of living.
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.