Are there serious proposals to just add a wealth tax on top of the existing income tax that would apply to the sort of people who actually pay much in income tax vs capital gains? It's an honest question; I haven't seen proposals of that sort, so I'm skeptical that the arguments are meaningful here. For an individual like Jeff Bezos, he's paying virtually no tax under the normal income tax rates referenced in the article, but rather capital gains tax, which tops out at 20%, not 37%.
None that I've seen, though I'm sure somebody somewhere has introduced something.
All that I've seen are wealth taxes on top of some arbitrary (but very large) wealth level. The latest proposal from Congress applied a 2% tax to wealth above $50 million with an additional 1% (3% total) on wealth over $1 billion. Plus a 40% exit tax to stop them all from fleeing to the Bahamas or Monaco.