Let's make some real calculation: Each month, you borrow $100 to buy food, and those $100 goes to the food company as income, and food company put $100 to bank, and bank loan out $90 (10% reserve requirement) to another borrower, he spend all $90 to buy products from your employer, your employer have $90 income, and he is so generous and gives you all $90 as salary. So, how could you payback your $100 loan with $90 salary at the end of the month?
The reason these examples are stupid is that they assume that one person holds all the money in the world and that value can only be traded using that money. Of course, neither of those assumptions are ever true.
Ok, lets assume that 7 billion people holds all the fiat money in the world and value can be traded using those money. Did that change the way how it works? Putting billions of semi-conductor components into a CPU does not change the basic electrics theory that you can prove in a flashlight
Yes, because now I can produce something of value and exchange that for money that can be used to pay back the loan (and the interest).
If you can do that, the rest 699999999 people will also be able to do that, and every one of them will need more money than they had originally borrowed to do that, that still does not make the ends meet
The only way to make your ends meet is someone else going default. With this system running continuously, there will be more and more people going default, thus banks collect one dollar interest from you while lose one dollar from that defaulted guy, the result is still not able to sustain long term wise, since banks also need interest income to operate