Taxes on the rich are already at European levels in the US. There simply aren’t enough of them to cover current spending.
It is a similar issue with taxing nominal wealth. 2/3 of nominal wealth in the US is completely non-liquid. Taxing the liquid fraction is essentially leveraged as a result, causing a catastrophic collapse in the value of similar investments by ordinary people as a side effect. Impoverishing a large portion of the middle class to own the rich isn’t a recipe for political success.