You missed the question, so I'll ask it again: What happens if we just raise the marginal tax rate in every bracket to 80%? How about 90%?

It would have a devastating effect on people's marginal utility for income rather than leisure - and drive most of the economy into the black market - unless we returned to the more permissive definitions of what constituted taxable income and deductions that existed back when marginal tax rates for the highest brackets were that high.

Which is why it's a good thing we don't have to do anything like that. No country has ever had marginal rates at 80-90% across every bracket - that's just nonsensical. And while we used to have a top rate that approached those levels, along with a very small proportion of actual earnings that was taxable, we aren't going to go back to that.

Which is why I missed the question - I thought it was rhetorical. Why would you think that raising the marginal tax rate in every bracket to 80-90% was relevant?