It isn't, because the ultra rich have no capital gains. They get ultra low interest rate loans against assets so they never have to sell assets and trigger capital gains. Google "Buy, Borrow, Die" if you don't understand this strategy.
They have to sell eventually to pay off the loans. And if they die, their estate has to sell the assets to pay off the loans, and then their heir will pay inheritance taxes on top of that.
Unless their spouse is still alive. In the US, assets' cost bases are reset when a spouse dies. That is the main way that rich people avoid capital gains taxes. I'd much prefer simply stopping that cost basis reset instead of implementing a wealth tax.
They have to sell eventually to pay off the loans. And if they die, their estate has to sell the assets to pay off the loans, and then their heir will pay inheritance taxes on top of that.
Unless their spouse is still alive. In the US, assets' cost bases are reset when a spouse dies. That is the main way that rich people avoid capital gains taxes. I'd much prefer simply stopping that cost basis reset instead of implementing a wealth tax.