A priest does not “tell them to repent” at least in the manner such a short four word directive indicates. The Pope said do not push them away. He is the boss. He is also wiser than your average street corner preacher. He is said that holiness is stronger. Teach holiness. Teach reconciliation. Teach Church doctrine. Jesus never first said to repent. Even the most poignant example of the woman caught in adultery, he first helped her in her trouble. Then he showed mercy. Third, he told her to go an sin no more. All this was done* after* establishing himself as a friend to sinners, a feeder of the hungry, a healer of the sick and a teacher of truth.
In the parable, Jesus did not say what should be said or how it should be said. I do not know what you mean “mince words”, but Jesus did not always speak directly. He was not a street corner preacher yelling at passer-bys to repent. I can see that the Holy Father has found a good topic that needs to be taught to the “elder son.”
From the Holy Father’s interview
nytimes.com/2013/09/20/world/europe/pope-bluntly-faults-churchs-focus-on-gays-and-abortion.html?_r=1&
Pope Francis is trying to offer us instruction grounded in prudence on the right way of evangelizing without ostracizing.