these other assets like musk's stocks are still quite divisible, and theyre as liquid as the government wants them to be. just because musk hasnt written the liquidity into his government sponsored contracts doesnt mean the government cant say yes, 10% of your private spaceX stock is liquid and belongs to donald trump now
its real and thus it is taxable
Oh, are those real now?
Valuing assets is a routine, widespread thing.
You can't just handwave away the fact that the real world exists.
A painting can be valued. A vintage car can be valued. A movie script can be valued. My house's value changed a bunch during COVID; I'm still taxed on it! Each is an asset; none of these examples can be perfectly valuated; each may see its value change dramatically over time, but you can still estimate its worth pretty well.
Hell, I can put my house address on Zillow and get an estimate in real time.