I believe that the central cause of wealth inequality isn't so much about taxation or regulatory capture etc, as it is about individuals going to great lengths to maintain control of their companies. So someone can be worth a billion dollars with a 51% share but not be able to convert any of those stocks to cash, for fear of losing their power.
That's why they resist even a modest property tax on their stock, while the rest of us must pay property tax on our homes. This is self-evidently unjust and one of the major loopholes which allows the accumulation of extreme wealth while countless millions of people spend the entirety of their lives working to make rent under a negative net worth.
A possible solution to that might be to limit individual ownership to something equitable, say less than 1/3, 1/5 or 1/7 (my preference) of the total.
So a worker-owned cooperative could be thought of as ownership not exceeding 1/N employees.
That would give us a spectrum of possible structures rather than having to choose between the extremes of public and private ownership. Apologies if this concept already exists or is commonplace.