…over a period covering the last half millennium or so.
In 1458 the Ottoman Empire captured Greece and ruled it until 1832 when the (more or less) modern Greek state was created.
During the period of Ottoman rule, the Turks imposed heavy taxes and travel restrictions on the Greeks. They imposed property and trade taxes. They imposed the jizya, the “poll tax”, as they did on all other non-Muslims who did not pay the zakat. They forbade travel on horseback. The Turks took a lot out of Greece and put nothing in.
In 1832 following the Greek war of independence a German prince (Otto of Bavaria) came to rule as king of the Greeks. For most of the next 135 years the Greeks were ruled by mostly German kings. The first of these kings to be born in Greece, Constantine, didn’t assume the job until well into the 20th century and he was strongly pro-German. That’s why the Greeks were neutral during World War I.
In 1967 a military dictatorship took over and ran the country until 1974 when the present Greek state began.
Greece adopted the euro in 2001. While I think there’s a reasonable argument that the Greeks could have made better use of the last 40 years, the last 40 years isn’t Greece’s only problem. Greece has been systematically looted, misruled, and mismanaged, mostly by despotic governments over the period of the last half millennium. Changing the repercussions of that won’t happen over night.
