Now I’m going back to the original question, which is a good one! Why are Catholics leaving the Church?
I think you would have to look at some comparative statistics: lapsed Catholics in the 1950s vs. the 1970s, for example.
Certainly Vatican II was a factor. And Vatican II was not held in isolation. It was just one of many changes in society–worldwide–that came out of the early 1960s. But once again, people virtually never go back to the original documents. To give a relatively trivial example, the use of bells at the Consecration. Probably even relatively well-informed Catholics would say that Vatican II eliminated them, or that bells somehow “violated the spirit of Vatican II.” Nonsense.
https://www.ewtn.com/library/Liturgy/sanctusbells.pdf Trent had made bells obligatory; Vatican II didn’t mention them. The Missal of 1970 made them optional.
It was the interpreters of Vatican II who took optional things and either promoted them (new music vs. Gregorian chant) or eliminated them (bells at the Sanctus). There is a long list. And it divided people–pro-bells vs. anti-bells.
“Index of Leading Catholic Indicators,” by Kenneth Jones gives a good statistical examination of the exodus of priests and nuns. Why? My own opinion is that before Vatican II people became priests or nuns primarily for religious reasons. Those reasons were challenged. They realized they could be good social workers, nurses, teachers, etc. without being in religious life. Secular reasons (even if good ones) took primacy over religious ones.
As far as ordinary Catholics go, I suspect few have anything beyond a grade school or grade school catechism class knowledge of Catholicism. Those who went to Catholic high schools were taught WHAT to believe, but not WHY. Why do we believe Jesus is divine? Why do we believe in the Trinity? Why do we accept Biblical verses that most scholars think were added by copyists? All sorts of questions–and they were left unanswered. No wonder so many just walked away!
And, returning to the question of abortion, how many Catholics have actually acquainted themselves with the beliefs of other religions concerning the question of when a fetus become a human being with rights? Or the whole philosophical question of “what is a human being?” I suspect very few.
Finally–although you could make a much, much longer list–there is a prominent group (you see them constantly in these threads) who are obsessed with “sin.” For example, you see threads about “Is X a sin?” “Can I commit a mortal sin if I XXX?” If these people were teaching religion or RCIA, I think you would be wondering why there were so FEW Catholics leaving the Church instead of how MANY!