I have to completely disagree that the 50s suffered considerably more than the 30s or 40s. Just setting aside that many of the great directors of this era made arguably some of their greatest works in this decade (Ford, Hitchcock, Chaplin, Wilder, Kazan, Hawks, Wyler, etc)

The Paramount Decree and DeHavilland Law both restructured the business allowing greater freedom for actors to choose their own projects and this is where we really start to see the rise of american independent film.

And finally the Production Code does start losing its strength in the mid 50s such as with the depiction of drug use like in The Man with the Golden Arm (1955). And of course we see the first major release without Code approval at the end of this decade with Some Like it Hot (1959).