Wow, I loved this movie. And felt the social satire hit directly home, although I can see many people missing the real problem with the wealthy folks, how they are just as much “parasites” as the others. Perhaps that’s why you wanted it to be more clear? I prefer this approach— that just because you are ignorant, that isn’t an excuse.
I heard on /Filmcast someone complaining about the end of the film where the boy has a fantasy of making a lot of money and purchasing the house. The commentator (Jeff?) said that it seemed too obvious, that there were so many better ways to even fantasize about a solution. I think the final end displays the ultimate failure of our con-artist family. The son was the planner, the schemer. All of them acted, all of them improvised, but the intricate plans were the son’s invention. He was the writer/director of every scene and was integral to the success of their plan. What the final moments show is that he no longer had the ingenuity to make a plan any more. All he could give is vague notions with absolutely no detail. It is a “plan” destined to fail without even being tried, as opposed to his other plans in the film. The end of the film is how the family has nothing left to build themselves back up.