> ...You can borrow against it to get loans for money you can spend without paying taxes. ...
Are you assuming that loans don't need to be paid back at some point? What you're listing is ways of either investing wealth (that is, using it productively to make more wealth - which is far from easy or free of risk) or spending it down. Some ways of spending wealth down may be tax-advantaged in some locales, but this is offset by the fact that taxing income places an extra tax burden on the time-based and precautionary value of that same accumulated wealth. I.e. wealth that's being invested in a risky, long-term venture is in fact quite heavily taxed.
The rough tax avoidance strategy here is to take out loans with your assets as collateral, and keep rolling those loans forward until you die, at which point they can be paid off and then onto your heirs with relatively little tax. This doesn't give you access to all of your wealth as cash (since the collateral is risky so you need to put up some amount more than you're borrowing), but what you do get you get without paying anywhere near as much tax, the interest on such loans is very low, and you still keep control of whatever asset you're borrowing against and whatever gains/income it might produce.
> Are you assuming that loans don’t need to be paid back at some point?
No, what I said is you don’t have to pay taxes on those loans. Obviously a loan is paid back. The tax avoidance scheme here is that a loan is not income and you can use held stock (that hasn’t been taxed) as collateral for short term loans.
> this is offset by the fact that taxing income places an extra tax burden on the time-based and precautionary value of that same accumulated wealth.
Not sure what you’re referring to. Again, the mega rich often don’t have significant “incomes” from a taxation point of view, regardless of how much money they make or spend.