Yup. When rebooting, the assumption should always be that the audience has no prior knowledge of the character whatsoever-- like, if I knew someone who had never heard of Superman, then the movie should act as a perfect introduction to the character. With Superman, his origin is such an integral part of his character that the audience MUST have it explained, because so many parts of his character are focused around it.
If I was new to Superman and I watched SR, I'd be so weighed down with questions that I wouldn't even be able to pay attention to the story, and I think that's part of why it was not the success that Warner Bros. wanted. It was too steeped in nostalgia and made too many assumptions about what the audience knew about the character. The only assumption that the new movie should make is that it will be introducing Superman to a new generation, and that means introducing all of him rather than trying to throw people right into the middle.
IMO, watching Clark Kent learning to become Superman is worth the additional screen time it would take. People enjoy seeing how Clark went from being an abnormally strong farm boy in Kansas to a flying superhero in a blue costume, because it's interesting. Say what you will about Smallville, but how would they have been able to get the show picked up if the transition from farmboy to Man of Steel wasn't fascinating? (Of course, Smallville unfortunately dragged it out way more than it should have, and didn't even get to the fulfillment / pay off.) Not only is it dumb to assume everyone in the audience knows the Superman story, but also Superman's origins are too important, and too interesting to just say "been there, done that, throw away the lame old hat!"
