Taxing the value of non-liquid or semi-liquid assets is extremely adverse. The "value" of these assets is notional only, disconnected from actual liquidation which may have a much lower value ipso facto, especially if liquidation is forced to pay the tax on the assets. Furthermore, it can put many people in the position of owing taxes for which there is no realistic source of income to pay (like the proverbial grandmother's house). And then there is the vicious downward spiral in valuations of liquid assets this can create, as assets are dumped to cover the tax liability. The US tax code is bad enough as it is when it comes to taxing unrealized gains, doubling down on that would be profoundly stupid and would make many tech startups impractical from a tax liability standpoint.

All of which ignores that one of the (multiple) important reasons longterm capital gains are not taxed like income is that those investments are adversely impacted by inflation, which is not deductible in the US. In many other countries that tax capital gains at income-like rates, the cost basis is inflation adjusted, which substantially reduces the amount of taxes actually paid on capital gains. Most countries deal with longterm inflation on capital gains either by allowing deduction of inflation or lowering capital gains tax rates to compensate (which is viewed as simpler to implement), but it would very poor policy to do neither.

tl;dr: This is not realistic tax policy. See also: Chesterton's Fence.