Young man who believes in victory and glory, the homefront who is believing that they can win the fight: In the 1930 film, it becomes very apparent that the war spirit has not died yet.
The experience of making the 1930 version hit star Lew Ayres especially hard, and he became a pacifist. This came back to harm his career somewhat during World War II when, as general call-ups started to hit Hollywood as well, he sought to become an unarmed combat medic, a specialty that did not yet exist. The draft board could only offer him conscientious objector status, and an undeserved reputation of being a coward. He was fired from the popular Dr. Kildare series of films (the series was retooled into stories about Lionel Barrymore's Dr. Gillespie) and was unemployable for a couple of years until circa 1943, when the Army did begin to allow pacifists who wished to be medics to join without undergoing weapons training. He served in the South Pacific, which as anyone can tell you, was not a theater for cowards.
Ho Yay: In the 1930 movie, in the scene where Paul is comforting Kemmerich after Kemmerich loses his leg, is very heartwarming, and also very shippy.
Lighter and Softer: Compared to Johnny Got His Gun, another famous anti-war novel by Dalton Trumbo; this has led to many schools using All Quiet on the Western Front in curriculum over Trumbo's version due to Remarque's novel (in spite of its graphic imagery and downer tone) being less soul crushing and disturbing than Trumbo's novel. Also, Remarque was a famous critic of a totalitarian regime while Trumbo was a supporter of one, and Trumbo's work overplayed its hand beyond what was supported in history because it made the (plenty troubled but still democratic) Western Allied armies look worse than the German military under an authoritarian police state did in All Quiet.
Narm: In the 1979 film, the scene in which Paul catches a random soldier from the other side and stabs him...and proceeds to watch him for ten straight minutes (in real time) while the man just lays there dying with a goofy expression on his face. Possibly a commentary on how it was a fellow human being that is being killed for a pointless war, but still absurdly executed nonetheless.
Seinfeld Is Unfunny: The themes can look dated, because many other war novels and films repeated them.