I think that during FDR the upper bracket got to be 94%--at any rate it was all but confiscatory.
The GOP has been thinking of a flat tax--everybody pays a percentage. If you remember 50 years ago or more, you had to file and pay on even small incomes.
A flat tax probably is not politically feasible. People want deductions for mortgages and donations to charity. You are probably too young to remember but the government told the rich to either donate for a deduction or pay the amount in taxes. So the rich chose to donate to charities. If you abolish these deductions, foundations and other charities such as The Salvation Army, for example, collapse. Also, many lawyers and certified public accounts have businesses based upon a complicated tax code, which I think is something like 9 million words and totally unintelligible even to the IRS.
So the poor have no skin in the game, as the expression goes--that is, they pay not a penny to the general welfare of the country but get checks from the government. Currently, the high costs of welfare are unsustainable.
The tax code does need revision but it is difficult to enact. One way is to abolish some deductions in exchange for lower rates. Everyone who works should have to pay. The so-called negative income tax should be abolished. If you don't work, you don't eat.
What most of all needs to be done is to lower taxes on married couples. Women should not be forced into the marketplace so that other people can sit at home and draw welfare.
Finally, there are not going to be any major changes in anything until Obama resigns or his term expires. He has a veto power on all legislation that does not fit his progressive/leftist agenda and the remnant of the elected Democrats nationwide are mostly hardcore leftists who support Obama until the end of their lives.
It is a stalemate, but it cannot endure because it is not based on any reality.
2 Thessalonians 3:10 (KJV) For even when we were with you, this we commanded you, that if any would not work, neither should he eat.