This is much harder to evade - if you own most of Mayfair, you can't just move your assets elsewhere - they are very clearly tied to the location.
Of course, this would mean taxing powerful aristocrats, including the royal family. With their large majority, the British government had the opportunity to do this, but decided to take an easier path. The reason why this path was easier is now becoming clear to them.
Simple, and more effective!
As an example, Wouldn't that mean that if my startup raises a round of 1m for 10%, my NW would go to 0 to 9m. 6% of that would be around 0.5m, and 30% tax would mean I would have to pay 162,000 EUR in taxes.
As a cash poor founder how do you suggest I pay that.
That's why taxing income and not wealth has been the norm.