That would only be true if everything written before Vatican II was false. Obviously that’s not the case. According to author Theodore Sturgeon, 90% of everything published at any time in history is a waste of paper. That was true before Vatican II and is still true today. The 10% that’s worth reading is what survives the test of time. Recent books haven’t had a chance yet to be tested by time. So there only seems to be more junk published these days than in the past. Truth is, most of the junk gets trashed by history and lost, so most old books that are still around are actually pretty good by now. If you find any pre-V2 book that has an imprimatur, it’s almost a sure bet to be worth reading, not because it’s pre-V2, but because it’s old enough to have survived Sturgeon’s Law that 90% of everything is junk.
Also, keep in mind George Santayana’s line, “Those who do not remember the past are condemned to repeat it.” This applies to theology too. If you read only modern works, you’ll unwittingly commit ancient errors. This is a tragedy of the New Age movement: It’s mired in old errors because those involved in it refuse to look beyond yesterday. It has no historical sense. If it did, it would have more theological sense.