Those are all loopholes we could patch if there would be political will to do so. Unfortunately they're all rich fucks themselves and beholden to the donor class

Wealth tax. More specifically, a securities tax: a tax on the stocks, bonds, and other financial assets used to build wealth.

Payable not in dollars, but in shares of the security. Every year, the SEC transfers 1% of all securities to IRS liquidators, who sell off those shares slowly over time. Liquidated shares may constitute no more than 1% of total traded volume at any time period.

Natural Persons (as opposed to artificial entities like corporations) may exempt up to $10 million worth of shares from taxation. This makes securities - the "means of production" - much more valuable to the working class than to the ultra-rich problem class.

A securities tax is the only feasible way of effectively taxing the ultra rich. As you noted, they easily avoid both income and capital gains taxes. A direct tax on their wealth-generating assets pushes those assets out of their hands and I to working-class portfolios.

We also need to increase the capital gains tax: it needs to be considerably higher than income tax.

And we need a punitively high top-tier income tax rate, like the 91% rate we had in the 1950s. Nobody will ever pay that tax: they will avoid it either by lowering their revenue, or increasing their deductible expenses, like payroll. Better for them to spend it on something they can use than just giving it to the IRS.