Tax is undeniably complicated, and I have no firm opinion what is better, and I'm often shocked when people do. The regressive nature of a sales tax is bad, but then, income tax is so easy to avoid. We all need things, making sales tax almost unavoidable, and what's the point of being rich if you can't spend it?

The problem with income tax is that it encourages the richest to run scams where the ROI is "cost of accountant + tax saved < expected tax = do it". If your income exceeds $100,000, it is almost guaranteed to be worth it to hire expensive lawyers.

Then there are the terrible scams like the one I read (which I can't confirm) where startup founders with public companies receive a minimal income, like $1 per year, and instead borrow their yearly requirements against the value of their shares. That could be $10M tax free - it is borrowing so it isn't income - and a sales tax starts to look like a pretty good idea! That'd be $1M in tax on a sales tax of 10%, vs $0.

Anyway, like I said, tax is complicated!