Massive wealth doesn't operate in income or even in typical capital gains advantages you're referring to. It operates at a scale where the value of the assets are so great, banks compete to give loans to them, which are not taxed like income.
It's totally absurd to argue that loans from assets isn't income. It's used to purchase more assets, to purchase tax favorable legislation, to buy media to keep us thinking this issue is about paying capital gains on your retirement portfolio.
If Bezos will "never get that money unless he sells stock" was a true statement, then where do all the yachts and houses and other assets come from? How does he buy them? If the IRS suddenly recognized loans taken against asset wealth or any exchange of assets as income, the tax rates of the super wealthy compared to the average American would suddenly look sane.