There is a noticeable difference between the average superhero comics from the 80s and beyond and issues starring the same characters from the 1950s and 60s, and that difference is all thanks to the Comics Code Authority.
The Comics Code kept writers and publishers from printing anything that could be considered immoral or remotely offensive, and their assault on comic books began with the release of Dr. Fredric Wertham's book Seduction Of The Innocent.
Susana Polo of Polygon's Issue At Hand discusses the silly effect the Comics Code had on comic storylines, touching on how writers fought back with the power of morally neutral absurdity and how Nixon and Stan Lee helped cut out the Code.
-Via Polygon