I also reckon that there's no way the rest of the EU can (or would be willing to) help Greece into a better place?
The EU would disagree.
The way you describe it, it sounds like a bunch of people from different walks of life renting an apartment together.
A better way to look at is as a bunch of feudal states that have been engaged in continuous warfare for millennia deciding they'll let the bank manager tell them what to do. It never would have happened without the Marshall Plan, whereby a bunch of New Deal American democrats chose to remake Western Europe in their own image. American influences replaced a lot of the Hapsburg shit but at the end of the day, Europe has not been a particularly unified place.
Fundamentally, there are economic advantages to a common currency and umbrella trade agreements. Those advantages, however, are neither uniform nor universal. Thus, the Greeks blocking Macedonia by whatever means necessary.