There are several things here, so let's separate them.
Greece has not been able to successfully and efficiently run their own affairs, including the economy since 1821. Entry into the EU was rushed, partly on fake numbers Greece gave the EU, partly to forge a union with a common currency (monetary policy) but with dozens of different national economic policies. The drachma was exchanged at much higher value than warranted too. Many Greeks felt rich almost overnight. Many Euros got tired of Greece's behavior, especially the newly elected Syriza's rhetoric and amateurish stance. It was punishment time. Since the 1980s, Greece thought it was smarter and could fool the EU. Payback was almost natural when the Greek state went bankrupt. The austerity package was badly planned and implemented. It has turned many Euros (for different reasons) against the EU. Extreme parties became stronger (not a good thing either). Greece became a lab animal on life support and with no recovery in sight Greece remains badly managed by her own leaders! Let's say I was rich enough to pay off all of Greece's debt. So no more crazy austerity or capital controls. Is anyone confident here or anywhere to assure me that this mess would not happen again?...