You can rent out real estate. House hacking, Airbnb, boring rental, etc.

And you can sell otherwise non-revenue generating assets if you need to.

If you want to say it's difficult to tax illiquid assets, that's fine. But it's not impossible and while it would just change people's relationships to these types of assets (maybe in a good way for society), it's not going to be the end of the world.

Sure, and the rich person can charge people to look at their valuable artwork.

Rich enough to have money that can be taken away, not rich enough to afford a specialist for tax evasion. People like this pay most of the tax.

And yes, all the reasons why "taxing X would actually be harmful for the economy" somehow magically do not apply to the small fish.