I'm Greek myself and several of the situations the characters face in the movie are very familiar to me. The father enjoys ultimate and unquestionable respect by the members of the family. The mother stays passive, her role confined mostly to everyday chores. The kids are obedient little soldiers. Any thought of rebellion is suppressed by deep fear. These are all things I've witnessed and heard of myself, from friends and relatives. I remember various incest rape cases having surfaced through the years - they still do.
Avranas took his story to the extremes, to point out how rotten the institution we call the "holy Greek family" is. The apartment door is locked. To a patriarch, it doesn't matter what happens behind it, as long as it stays there. It's his family after all. What matters is his own face to society, to keep up appearances. What matters is the surface, not the substance.
I've heard so many women in my life saying "Oh yes, he may beat his wife up, but at least he doesn't cheat on her!" or "He may cheat on her, but he always provides food for his family!" What is pictured in the movie is the continued victimization of the female. The woman is rendered to an object for pleasure, for cooking, for cleaning, anything to satisfy the primary male in the family. The father must be obeyed and respected at all times, even though he's an unemployed middle aged man who can't provide much to his family - and this will not be questioned either: he's the MAN. It's so deeply ironic that the song he forces his little girl to dance to is, in fact, feminist at best, and a hymn to misandry at worst (https://www.youtube.com/watch?v=rwbYEOKzBYo).
The females have learned to accept their degradation as something normal. The oldest daughter feels numb, not being able to wake up to reality. Her kids, her own brother and sister apparently, she knows will go down the same road themselves. When one of them understands the true nature of her family relationships, she commits suicide. Again, the family's priority is to save face - it was an accident, not a suicide.
This attitude, so prevalent in Greece until recently, is what I believe is the director's target here. Some scenes may be hard to watch, but he didn't really cross the line that much, or as far as he could have. From the moment I realized what was going on, the story made sense on so many levels, I was really at awe with what the director accomplished: a film that's both a psychological thriller and a cold, yet in-depth cultural study.