In theory, maybe, but in practice that is not what happened over the past decade(s). Instead our retirement funds are paying it back.

When the market grows it makes the collateral worth more, which lets the borrower keep refinancing the debt instead of selling assets and realizing taxable gains. As long as the assets appreciate faster than the debt grows, the borrowing can effectively roll forward for decades. Eventually the estate pays the debt out of the assets themselves, but this is not necessarily out of taxable income earned during the person's lifetime. The US markets has seen exceptional genuine growth, but the trillions of 401(k), IRA, etc money flowing in to them over the last 40 years is no small consideration.

And even so, you could say it all settles out in the end, but that ignores the fact that there have constant constant efforts (and successes) in eroding away the e̶s̶t̶a̶t̶e̶ ̶t̶a̶x̶ "death tax" during this same period.