The debt it high because what was supposed to happen in the past 70 years, is all of a sudden happening now. So if you spread the debt over the 70 years (growth related), you would've finished a few projects in the 60's, 70's and 80's, and post going live, you would've captured income which would've offset the debt over the years (decades and that too like 6-7).
So all things are being tackled in this term of the local government. Electricity, Infrastructure, CPEC, Privatization, Tax system overhaul, Metro projects, Airports, Port Operations Expansion, Military Ops in FATA, Power plants and alternative energies, Healthcare, Education, Industrial expansion, etc, etc, everything has been ignored for the past 7 decades.
You won't find a country who just in on 5 year terms deals with all the above things. So its almost like Pakistan was born in 2013 and now its the first government doing all this work to a new country. So naturally debt will be higher. But by 2020, the Pakistani economy would be over 600 - 700 Billion (GDP), so a $ 150 billion debt (being slowly paid off, would be 15% of the GDP). Which isn't bad. Growing countries could have up to 40-50% of debt. India ran on 45-50% of debt for the longest time, and still has high debt. That's how a poor country grows and establishes more businesses and expands infrastructure and economy!