Criticising interest itself is kind of meaningless. I agree with that, but if you think about It the interest rate has a tendency to go to zero on its own. Positive interest indicates that that the future economy will be larger if money is invested in the present. If you have an aging economy you can't expect the interest rate to be positive. So the argument should be in favour of complete capital markets with positive and negative interest. During a boom you expect positive rates and during a bust the rates would be negative.