"Buy, borrow, die" is a bit of a bogeyman of the Left; it's not a common strategy for HNW or UHNW individuals, and to the extent it is used, there are much better ways to close it than a wealth tax, which is coarse and rife with implementation issues.

The main implementation issue with a wealth tax is that it doesn’t at all interact with the capital gains tax. It’s easy to fix the implementation issue by integrating the wealth tax into the capital gains tax (call it unrealized capital gains tax for starters), make the tax refundable when an asset loses value, and netting it against the actual capital gains tax.

With this framing, the wealth tax isn’t a new tax; it is only prepaying the capital gains tax instead of allowing it to be deferred forever.