Not surprisingly, back when marginal rates were so high, rich Hollywood actors also hired CPAs to avoid giving 90+ percent of their income to those in power. The previous discussion on this was here: https://news.ycombinator.com/item?id=19031135
Did they not pay because they had magic deductions or did they not pay because of sabbaticals and reduced income? Because the former means it was no better than today (and income differential stats around CEO vs line-level employer suggest this is not true), but the latter is by its very nature better than today. It's literally creating more opportunity for more people to earn money? If person A isn't doing the work and making the income, person B is. So inequality will be less!
That high tax rate disincentives a small set of super-high-earners from running ever-more parts of the world? Good!
That's not how things work in reality. Whatever work Jeff Bezos decides to not do as a salaried employee doesn't get distributed elsewhere, because he derives almost no income from his salary.
When someone says "simplify" the tax code - well firstly, this has never happened. A simplification is an amendment, and the tax code gets larger - they've never actually managed to shrink the size of the law there.
But then you get to decide: which exemptions and deductibles are you getting rid of? For who? Because if you want to simplify it, that's what's actually got to happen.