debt as percent of GDP
is an excellent metric, in a normal healthy economy. But if there are severe distortions, like when the expansion is mostly financed by borrowing, this can get tricky. The much touted 6% growth during IK's tenure was mostly consumption based on borrowing + remittances without a whole lot of increase in production. Now that inflow has gone down, everyone is shocked that there is no growth. If Pakistan had a large GDP and CAD was a small part of tradeable, that wouldn't be a problem. The present situation is the extreme example when external debt gets unsustainable: Simply no new dollars available and the economy comes to a screeching halt for lack of imports.
You should read the Our Dutch Disease
by SBP Deputy Governor; https://www.dawn.com/news/1724225/our-dutch-disease
Put in simple terms, what he says is, borrowings + remittances have bred a sort of Welfare Dependency
that we see in Western societies where some people are simply not interested in working and subsist on transfer payments.