I’m aware of the system, but all you’ve done is explain how the tradeoff works. It’s also how governments raid pension coffers to pay for something else like infrastructure (see Illinois). I’m not claiming I receive “my” money in SSI, but I am saying there is a point beyond which the system becomes untenable. At some there is a tradeoff because the money is gone. You could raise taxes or pay interest on a new loan, but again, that only works when there’s still confidence in the system. What happens when there is no longer confidence? Interest rates become untenable or the citizenry will not continue to support additional taxation.

Now I will agree that this is a contrived problem because SSI is a contrived system. We could just change the rules and make it continue to work, but that will come with tradeoffs.