Taxing unrealized capital gains is possible, but it's not clear how you'd do this without destroying the entire financial (as opposed to goods/services) economy, since taxing 'wins' without crediting 'losses' makes any margins-game like investing impossible, but billionaires receiving billions of dollars in refunds when the market crashes is probably not visually great. It also seems fairly certain you'd introduce investment hedge possibilities with this, which is also probably undesirable. Not an easy problem.
And of course on top of all of this there's the Norway Problem. [1] Norway decided to introduce a hugely unpopular increase to their wealth tax system. It was expected to increase government revenue by about $146 million per year. Instead it resulted in a loss of about $448 million per year. Make taxation sufficiently onerous and people will simply leave your country. We're not talking about a captive audience, especially in modern times.
[1] - https://www.brusselsreport.eu/2024/09/11/the-failure-of-norw...
But anyway, lets focus on the low productive people, because that really what is going to bring America out of the rut that it is in. Not the overly powerful rich that are totally screwing the regular joe. You're on another planet bro if you think the problem is the low productivity person and thats what America needs to focus on right now.