When the state's debt growth is unbounded with the feature (not bug) of money printing and suppressed interest rates, eventually that printing and spending outstrips the real economy's ability to extract and utilize resources to generate value; people are unable to produce faster than the currency can inflate. Thus, you then have a net negative economy, where the state's deficits are consuming all newly generated wealth PLUS the wealth generated by previous generations. An inflection point. A country begins to quite literally eat itself alive.