Interest rates should be proportional to the wealth of the borrower.

Need 300k to buy your first house, that is a necessity for you as a human being to live in? 0% annual interest.

Oh, you need to borrow 40millions because your mega-yacht is running out of Caviar and you want to build a massive luxury resort destroying half a reef in a tropical island? No worries, 300% annual interest.

Fixed.