How can that be?
Look, Superman's hard to get right. He's just so much - better - than we are. Name a talent, he's got it. Name a weakness, and he doesn't. He belongs to a simpler, less cynical age - even his costume is made of bright, primary colors. (Notably toned down in this film.) The character has a fascinating history - and the fate of his creators Siegel and Shuster is a cautionary tale in its own right - and, with 75 years of backstory for Superman, Man of Steel had a lot of material to pick from.
But you have to pick. Man of Steel can't quite decide what story it wants to tell and therefore, it tries to tell bits and pieces of too many. While I quite enjoyed large chunks of it, the movie didn't satisfy me. It's cotton candy trying to be a Sunday dinner and it confuses length with quality. You have some fine casting (Michael Shannon as Zod, especially) and some memorable scenes, but you also have sizable internal inconsistencies in the story, some seriously clunky dialogue and a basic misunderstanding of who Superman is at the core - and that just won't do.
The best part of the Superman character isn't the powers. It's the hope he provides - that the human race is indeed fallible and error-ridden, but that we have tremendous potential; that we are, in fact, worth saving. In Man of Steel, there's a wonderful scene featuring Perry ("Great Caesar's Ghost!") White and Daily Planet reporter Steve Lombard staying with and trying to rescue a trapped Jenny Olsen. It'd be simpler and probably smarter for White and Lombard to flee the carnage, but they stay and try to help. Superman's nowhere around. Actually, that's not quite true - he's partially responsible for the collapsed buildings that are crushing the trapped Jenny into cub-reporter-jelly. See, Man of Steel is a bit bloated time-wise, in part because Snyder opted to keep in lengthy fight scenes that are fun to watch at first, but become repetitive and are conducted by two super-beings with no regard for the millions of humans who call Metropolis home. From Zod, we get that point of view, but Superman should have the sense to take the fight away from a crowded urban area.
Also - Superman doesn't kill. That's a constant and don't mess with that. Don't even try to argue this point with me - it's not justified in the film. I think the Nolan crew figured that they had to go dark, and you don't get much darker than that. They are wrong.
In a way, I sympathize with Snyder/Goyer/Nolan's problem. There's so much to choose from - Superman as Moses in a space-reed basket, Superman as Christ figure (framed by stained glass at one point), Superman as confused kid, Superman as bull elephant, battling for supremacy while totally ignoring the devastation his efforts are causing, Superman as product placement (Sears? Really? Although the Lexcorp logo and the Wayne Enterprises satellite were nice touches), Superman as Nietzschean "ubermensch," but it seems as if at some point, they threw up their hands and said, "There's no way to tie this all together. Just blow stuff up. And use handheld cameras, so it's shaky enough that no one really notices the plot holes because we've made the audience queasy."
That's sloppy storytelling. And even with a budget of well over $200 million, it's a cheap shot.