The only way to get rid of tax avoidance is to simply tax transactions, every time, for every person, on every transaction.

“Oh, that’s regressive” they will say.

Make it small per transaction. A rich person spending 100x what a normal person spends will pay 100x as much tax. A billionaire spending 10000x what a normal person spends will pay 10000x as much. And they will also be taxed if they borrow money (that’s a transaction) against assets so they don’t have to sell them.

And when someone inherits, that’s also a transaction. Money moves from one person to another. So that same tax applies.