One thing that I miss about older Pixar films is how extraordinary the writing used to be.
It's usually still pretty decent (TS4 and Soul being recent, pretty good standouts), but man there was a magic formula to pretty much everything Toy Story 3 and earlier. Classes could be taught on how layered and tight the screenplays for Wall-E, Toy Story, Ratatouille and Monsters, Inc are. There's not only an emotional core to them, but they're also whip-smart and funny as fuck (especially the first couple Toy Stories and Monsters, Inc). I miss that, man. I'm glad other folks like Sony Animation Studios have been stepping up to the plate recently.