Even if people do vote for corrupt politicians, and even if a significant share of the population has probably benefitted from or taken part to corruption, it is still absurd to hold people directly responsible for it. These kind of systems, once established (and their establishment itself generally comes from inherent societal factors), create dependences which make them very hard to break up.
This is true but irrelevant. It is always the citizens of a country that suffer the consequences of it's incompotence... even places like North Korea. If the North Koreans are to suffer for the incompetence of their horrible regime, I feel no pity for Greeks suffering the consequences of incompotence by their elected government.
Sure innate structural factors that the Greeks did not choose are responsible. You can say the same thing when it comes to individuals... is the serial killer to blame for possessing a neurology or suffering an upbringing that primed to murder people? No, nonetheless we punish him because no quantity of philosophy can overrule the iron law of society: people and groups are responsible for their actions.