Sir, Lumen Gentium did not change anything.

Anyone who knows the truth and yet rejects it, cannot be saved.  The difference before the Reformation and after the Reformation is that it was presumed that anyone who wasn't Christian knew that Christianity was true and still rejected it.  

The presumption that Jews and Muslims know the truth yet still reject it is what was incorrect--not the teaching that those who know the truth yet refuse to reject it.