Perhaps having billionaires is evidence of an inefficient system--I am not pushing back on this idea.

But your imagined idea is quite flawed. The Trillion dollars held by billionaires is not just sitting there. It is invested in creating new businesses and other things that generate ROI. Now if instead we use that to pay min-wage salaries those folks will buy basic goods and services. The WONT invest it in the next business.

So if we make this shift we are essentially shifting a greater fraction of today's GDP into current consumption today, and less into building for tomorrow.

Of course if the billionare buys a super-super yacht then it IS the same effect, GDP is spent today. but much of the rich's spending is really investing to have even more money tomorrow.

Now you could argue we should tax the billionaire and put the proceeds into a sovereign wealth fund for the USA. that would be different, that would still be investing in tomorrow.

But as you frame it, you are really just arguing to eat all of our food today, leaving little for tomorrow. (e.g. if we really took your approach to an extreme, and taxes all wealth anywhere beyond say 10x the median savings in the US, there would be almost no money available to invest in the future. the economic growth would slow to a snails pace. (of course you could tax the rich, and then REQUIRE that all citizens save 20% of their income for their retirement. That would keep the economy humming) but however you do it. Somebody better have a huge HUNK of money they are investing.