Which movies do you believe were immoral in the 1930's through the 50's that should have been condemned by the Legion of Decency but were not?
Well let's see here; "Comrade X," "Why We fight" series, "How to Marry a Millionaire," etc. Hell let's face it pretty much every Hollywood movie has been immoral. There was no "good old days" in Hollywood.
I do not know much about the Legion, however, you are 100% right. There were no good old days, and pre-code films were just as objectionable as any now, and the Code films presented often a very distorted reality.
I do not know about the Legion, but I would not expect any organization to be able to condemn everything worth condemning. These days, with the Internet, it is much easier to get good reviews, rather than relying on a single group to do it.
I also think most films could easily be condemned on moral grounds, and that anyone judging them might be subject to relativity, as many films were edited to gain ratings. Even now, directors will add over the top scenes, just so they can cut them later and get the rating they wanted.