Problem is the uber wealthy aren't actually PAID that much. They're given stock options or other, non-liquid cash, which isn't taxed as income. It also doesn't get taxed until you withdraw it (see the capital gains "scare" that the media hyped up over the recent changes to tax code). Had to dig a bit to find it, but Quebec provides their people with >1mil income per year, which is about 7,000, or 0.08%. Extrapolated to Canada-wide (which I'd argue is not accurate and way too high) gives us 27,000. That's not a lot of people to try and draw any major funds from. Especially at a ramping rate of return like proposed.

Very rich (bezos, Westons, etc) then draw it out as needed, or use it as collateral against loans at lower interest rates than their return on investments, driving things like private equity, corporate landlords, etc. This then cycles, increasing their paper wealth while not actually having a lot of income to tax easily.

We should de-incentivize wealth hoarding

I agree. The problem is how to do that without penalizing the bottom end, overcomplicating tax laws further, and/or creating some other loophole for the rich to jump through. What counts into your wealth hording? Property? Investments? Are unrealized gains (ie stocks worth a ton but not yet sold to gain actual money) counted against them? What about property - if the market skyrockets, are people forced to sell their homes?

What about things like the wealthy transferring their extra wealth to children or spouses? How does that play into it? Its messy once you get into the details of it, and those are the key points that would actually make a difference.