You could peg the numbers to inflation.

Personally, I see a big benefit of a wealth tax being lowering wealth inequality; even if the money isn't actually used for anything useful. That would at least help prevent the ultra wealthy from being able to unilaterally ruin society.

They can't ruin society unilaterally, unless you're talking about Vladimir Putin, who can only do it because he's the head of an autocratic socialist state as well as potentially being the richest man in the world. But the rich bit isn't what does it.