> If they don't then the money disappears from the system, but in most booming economic times, more money is created, and eventually more money is printed to provide more base money in order to pay back all that interest.

The financial systems works different.

You seem to be conflating wealth and money. Money doesn't disappear from the system when someone fails to repay a loan. (Unless you are taking a rather wide, but still sane, definition of money, and hold that lending increases the money supply.)

No extra money needs to be printed to pay back all that interest. That's because central banks pay a dividend to their governments.