As far as Superman films go, Man of Steel isn't actually all that bad. Sure, it might be littered with Snyder-isms right across the board, from obtuse Christ-like imagery to bloated, overinflated and computer generated fight scenes, but it's not as soulless as one would think.
The problem with the film, fundamentally, is that it's suffocated by the very obvious intention to mark a severe course correction in Superman's filmography. Each and every last cinematic outing to have featured the Last Son of Krypton had made a point of placing the character's symbology front and centre to their proceedings. Action wasn't so much a priority as it was an addition to the bread and butter of the films' stylistic attempts to echo the Fleischer Studio's shorts of the forties and fifties, and so WB - anxious to avoid criticism that their next Supes film could be considered 'boring' - went all in with a director who could (in theory) make a Superman story with plenty of thrills, spills, and Kryptonian space drills.
The resulting product conjured a bleak and emotionally distant incarnation of the Superman mythos, with Henry Cavill in particular missing the mark as Clark Kent. Further to that was the film's controversial climax, which contradicted any kind of optimism conveyed by Hans Zimmer's wonderful (and overlooked) composition.
WB made the right move in electing to use the Man of Steel as a means of kickstarting their shared superhero ensemble, but it lacked balance. Of course fans want to see Superman duking it out with crazy powerful enemies, but he needs a heart too. Laying the foundations of your universe on the bodies of thousands in Metropolis just wasn't the way to go.