An excellent article from Fr. William Most on EWTN has relevant discussions for Vatican II. (Linked Here)
One of its final conclusions;
“Following proper theological method, the Fathers and the Magisterium saw two things: a)the Church is necessary for salvation; b)In some way God must make provision for those who do not find the Church. This was already stated in Romans 3.29 by St. Paul. If He did not do that, He would act as though He were not their God- He would condemn millions to hell who never had a chance!. Such a God could not be a God at all, but a monster.“
So what is the heresy of Feeneyism that the Church as condemned. That a water baptism is the only way to be saved. It is a strict interpretation of outside the Church there is no salvation. Feeneyism denies a baptism of desire (one without water but through conscience and actions often involving invincible ignorance)
Vatican II often talks about how those outside the visible (not invisible Church) can be saved. These texts have caused much controversy. It would be good to recall that the Church has explicitly condemned the idea that only water baptism can lead to salvation and that baptism by desire does not happen. The Catechism of the Catholic Church mentions this topic in paragraphs 846 and 847 quoting from the very document which condemned the Feeneyism heresy.
Thus, when Vatican II talks about baptism of desire for Muslims or Jews or for other religions do not be so hasty to think that Vatican II is therefore wrong.
The article linked from EWTN goes into great depth contrasting different quotes from Popes and Church Fathers showing that only a selective use of Church Father quotes says that baptism of desire is not possible, while a broad and full understanding show that the Father’s held to baptism of desire. When they seem to disagree there is often reasons and context that show that there rather strict sentences do not contradict baptism of desire because they were only speaking of those with moral culpability (not ignorant).
Did you know that baptism of desire even goes as far back as St. Ambrose?