If you borrow the very first dollar into existence, but promise to pay it back with another dollars worth of interest, where do you get the second dollar? How do you pay it off?
By making more debt from another party. The entirety of today’s economy is based on creating more and more debt. Because of interest, you have to create more debt, there is no way around it, and this cumulative debt grows and grows, until the entire house of cards invariably collapses.