Take the gold standard, do you think anyone was able to borrow gold and pay less back? Isn’t that the actual interest rate we are discussing here?
Gold in a free market would tend to self adjust.
Buying gold as an asset when there is a "flight to safety" and then selling it in better times when there are enough other good assets available such as stocks with good dividends would mean buying gold when gold prices are high and selling it when prices are low thus resulting in negative returns.
Negative real returns happen in free markets. Blocking them causes huge problems.