I think Paul VI’s stance against artificial contraception was the defining moment of his papacy, and had no parallel under JP II. While JP II did give us Cardinal Ratzinger, in the US Church the Cardinal was the scapegoat for the continued conservatism of the Church; JP II was slow to enforce orthodoxy in the US bishops and it was left to Ratzinger to do so.
Reform comes slowly. Consider how long it took for the Council of Trent to meet after the popes overcame their antipathy to councils and agreed to call one. But the situation in the United States was more like that in England when Queen Mary to the throne. Under King Edward, the Protestant party led by Cranmer has instituted radical reforms which went against the grain of the people who were still largely Catholic in sentiment. This is why the Queen , led by her kinsman Cardinal Pole, dared to resume relations with Rome. But there was still a large Protestant party with which Princess Elizabeth was still tenuously allied. But in the United States in 1979, the bishops were mainly “reformers.” There was no equivalent to Cardinal Pole. If Mary had lived another twenty years, probably Elizabeth would have turned Catholic, maybe even married her “Robin.” But “ifs” don’t matter in history.