Humani Generis was intended to say "No" to the sorts of approaches represented by la nouvelle theologie, but it was modified, according to de Lubac, who had a letter from John XXIII on this, stating that Pius XII had himself altered elements in Humani Generis that were directly critical of the kind of work de Lubac was doing.
Is that why he joined the other "experts" of modernism at the Council--men like Courtney Murray and Schillebeeck? I don't buy it. The New Theology was lethal to the faith. Pius XII knew it and he said so, condemning the very men who became the leading lights at Vatican II. Is it any wonder disaster followed within ten years? Humani Generis still stands as a warning, though you'd never know it in the contemporary Church which glorifies what had been condemned.