You force the founder to give up their private property just because it is valuable?
Remember these are not dollar bills in the founders bank account. It is just the company they created is now very valuable. It does not mean it is liquid.
Which party is the IRS partisan towards? What do you mean by partisan?
That's how taxes work.
On the business income, on the sale of shares, on their wealth, on loans, on estate and inheritance, etc.
Breaking up the company is another avenue, it could increase competitiveness and make the markets freer, open up more options for employees to shop around for employer, etc.
Raising minimum wage, stronger overtime rules, paid family leave, mandatory paid vacation and sick leave, non-compete restrictions, profit-sharing requirements, and other regulation that favors the employee is yet another avenue...
There are ways if the will is there.
Owe 1M$ in taxes and have ownership stakes in a company worth 1B$? Fine, transfer a 0.1% share of ownership in the company into the SWF.