This is what parrots continuously say while ignoring that the original problem was that in the existing system they not only don't pay taxes on the money they don't spend, they don't even pay taxes on the money they do spend, because they can borrow what they want to spend instead of using taxable income and then defer capital gains or keep assets in shell corporations.
Getting from that to where they at least pay the same taxes as anyone else on the money they actually spend would be a marked improvement.
We already know how to solve that one though. You now have corporations and billionaires actually paying the consumption tax along with everyone else, so you take that money and use it for a UBI, which causes the effective rates on lower income people to be much lower or even negative even though everyone is still paying a uniform marginal rate.
Getting from that to where they at least pay the same taxes as anyone else on the money they actually spend would be a marked improvement.