What, pray, can you expect from the Oscars? The Academy are all Americans, and Americans are, on the whole 'small-c conservative', so anything experimental is suspect. They try to be 'high culture' and promote 'film as an art', so anything too aligned with popular culture will be disregarded. On the other hand, they will always ask "Will it play in Peoria?" -in other words, is it comprehensible to white suburbanite America? If it's too heavy, intelectual, niche, genre or downright odd, then it can't be in the running. Then there's the whole 'Buggins's Turn" ethos as well as doing favours for your mates.
Cartoons were shorts, designed for Saturday morning Matiness to keep the kids happy while waiting for the main picture or the serials. Snow White and the Seven Dwarfs (a full-length animated feature! WTF?) was too experimental, and anyway a kids' film, unworthy of consideration on both counts.
As regards Citizen Kane, Welles was a newcomer, he hand't earned an Oscar yet. John Ford had been directing since 1917 -he was established and respectable.
Though Ford directed The Searchers, the film was too much of a departure from the usual Western. Wayne playing against character, and the ambiguous attitudes to the Comanche. Too much! The film leaves a bad taste in the mouth, especially with having no resolution.
Muhc of the same caution applies to Vertigo. Too deep, too dark and no proper resolution.
2001: A Space Odyssey and The Exorcist are unapologetic genre films. As such, they would be assumed only to appeal to a limited audience. If about 70% of the public is not going to see the film, then you can't reasonably dub it Best Picture.
Star Wars is not Oscar material, that's all. Despite the flashy effects and spectacle, it's no more than a Boys' Own, comic book, Saturday Matinee romp! Even as SF, it's as inferior to 2001 as Star Trek is to Babylon 5.
Everybody understood what was going on in Kramer vs Kramer, it was an expereince a lot of folk had been through and everybody else knew someone who had. Nobody knew what the Hell was going on in Apocalypse Now!
ET is a kids' film (see Snow White above.
The Truman Show, again, is simply weird! Most in 1998 would regard the premise as absurd. Others would be expecting Jim Carrey to start doing his Mask or Ace Ventura thing at some point. Too uncomfortable.
Remember, the Oscars is all about reminding everyone that Hollwood turns out the best movies in the world. Movies that show the world what America is all about, or reflect the experience and ideals of the people of America. It is not, and has never been, about the quality of performances or films. It's about assuring folk that everything's right with the world (ie America).
