True Significance [of Vatican II] IS
That it was fundamentally altering three convictions central to historic Evangelical objections, which understood (whether accurately or not) Roman Catholicism to hold:
1. an exaggerated exaltation of the Catholic Church as an institution whereby it communicated that the institutional Catholic Church was in itself a salvific agency serving, in an exaggerated way, as a continuation of the ministry of Jesus;
2. an exaggerated view of its sacramental ministry, seen to be the key to ministering salvation (either in baptism or in penance (described as “necessary”, D. 839, 894-896, albeit with the usual emergency alternative of the “desire of the sacrament,” D 898) or in the Eucharist);
3. “Rome never changes” and hence, until the Council of Trent’s decrees are explicitly renounced, all appearances of change are superficial at best.
All three points are implicated in one single decision taken at Vatican II: its acceptance that Protestants who had no membership in and no sacramental ministry from the Catholic Church were yet regenerated Christians. When one considers the change in the first point alone – termed by some as the Catholic “tendency most suspect to Protestants” – this is a sea change of huge proportion. With this change the focus has been removed from the institution itself as a salvific institution and switched back to the underlying Gospel message.
Source: Paul Miller - "Evangelicals Cooperatively Evangelising & Discipling with Catholics in Faithfulness to Evangelical Distinctives", by Paul Miller