If the % required to service it was growing significantly, that'd be a problem. The debt outstanding growing, on its own, doesn't matter.

The government is not a human who better pay off their debt by 65 or they're screwed. The government'll keep receiving income "forever", in a pretty predictable way. So there is no reason to ever stop borrowing; it'd be leaving money on the table (utility of a dollar now > utility of a dollar later).