Extremely short analysis. After 2008 Greece's GDP crashed by 50% over several years and stabilized 2016. It's pretty obvious that when you have a shrinking economy that your real debt burden is going up over time. 100% debt to GDP will turn into 200% and it's not because of irresponsible spending or low taxation.

If anything you have to lend more money to Greece and only give the most productive companies/sections of the government access to loans, if Greece's GDP was 355 billion € in the past it can recover up to that old level.