There certainly IS such a thing as "Pre-Vatican II" concepts when it comes to dogmatic teaching.  It deals with the APPROACH to the teaching and emphasis on that teaching.  In the 1950's, people were preached at from the pulpit [pre-Vatican], that if they eat meat on Fridays deliberately, they are committing a mortal sin.  In Latin American, at that same time, this was not a teaching at all.  So if an American, European, Canadian, Australian, New Zealander, etc---ate meat deliberately---that's a mortal sin.  But if a Mexican or any Latin American ate meat on Friday---it wasn't a sin.

Secondly, your comments of "rank relativism" is nothing but fear of anything modern.  There was no such definition as MORTAL SIN in AD 17,  or 1017 either.  YOU fail to see that the development of doctrines was evolutionary---plain words--IT TOOK TIME.  We didn't have either the terminology, the actual teaching, worked out from the beginning.
That one faith, baptism and church has changed over centuries.