I mean, they linked fiat to debt, after abandoning gold, because debt tends to cycle down under inflation and the resulting recession, as it's retired (because the debtor sells it below price or defaults).

Debt has a tether to the real economy. 

 Hmmm... Yes, when debt maturing > debt issued it reduces money supply, usually happens during high rates / recessions. But inflation doesn't discourage new debt. And ecb can print money to buy bonds from the market, which isn't new debt.