OK. I'll take a shot at it.
The famous Roman orator Cicero is given credit for coining the phrase: Justitia suum cuique distribuit. In English it means, "justice delivers to everyone his due." Often we see the Latin form shortened to suum cuique or "to each his own."
This is a common principle in today's world, especially in the modern neoliberal economies and politics. We see it in the proverbs of many nations as well. In English we have: "everyone gets their just deserts" for example. In German it is, "Jedem das Seine," a popular proverb, that was often used by the Nazis and infamously associated with the Buchenwald Concentration Camp.
Yet, in this parable, Christ offers a way of thinking that goes precisely opposite to that. The Father (whom we can associate with God, the Father or Abba) does not set out strict punishment of the wayward son. The older son offers the typical human response, suum cuique. "I'll go get the whip Dad, and we'll flog him good for what he did to both of us!"
But, the Father does something that surprises the eldest son and no doubt Christ's listeners as well. He throws a feast. He tells the older brother, "your brother was dead and has come to life again; he was lost and has been found."
I think the challenge is not to see it as just that parable but to find one's way towards being as the Father. Remember that Christ calls us to be compassionate as His Father is compassionate. That is no ordinary task! I look at it as a ladder. One is the younger son, then the older son, and finally one strives to be as the Father (knowing of course that perfection is not possible). Christ's call here is not easy, but very radical and very difficult.