That's true, but "much harder" != "impossible". If you print enough dollars, there will come a point at which it will stop being the world's reserve currency. The only way to find out where that point is is to actually cross it. That will be a very painful experiment to conduct. If we ever get to that point, the world will learn the meaning of the word "hysteresis".
No one knows what's the limit of "enough dollars". It's not infinite but it's very possible that enough money can be printed to provide ubi to the lowest rung of the society ad infinitum
There is no question that this could be done. In fact, I think that this is a fairly reasonable policy. It effectively amounts to a flat tax on wealth to fund UBI. Personally I would prefer a progressive tax to "flatten the curve" more at the top, but I'd settle for an inflation-based UBI.
But that is NOT what is happening at the moment. What is happening at the moment is almost the exact opposite: money is being injected mostly at the top in order to prop up asset values, with a little bit coming in to the bottom via the $1200 relief checks, and the middle via PPP.
That's right. Trickle down economy is not ideal. It was a worthy experiment and it has failed. It's best to give MMT a shot and provide UBI to the lower rung of the society.