Their take was Superman is supposed to be powerful to learn to work with it. Alan Moore sure did.
I personally don't see why it's so damned difficult to write about a character as powerful as Superman. As people have previously said, folks like Elliot S. Maggin, Cary Bates, Alan Moore, Marv Wolfman, Martin Pasko and many others were doing it for years before the overpriced "hotshots" of today started whining about how hard it is. Take a look at the story "How to Tame a Wild Volcano" from the Sandman saga. I know it was written by Dennis O'Neil, but just listen for a minute. Not a super-villain was to be found in this story (I discount the Quarrmer because he didn't really have that much of an impact on events in that issue). The story deals with Superman trying to save an island of villagers from an erupting volcano. Easy as pie for the Man from Krypton, you say? Normally, yes. However, what makes the job difficult is Supes having to do it while dealing with the island's knuckleheaded owner and trying to accomplish the job without trespassing and therefore breaking the law (which Superman is usually loathe to do). All this while trying to cover the event for an equally knuckleheaded boss (namely Morgan Edge) for WGBS News.
How do you write about a character as powerful as Superman? Like that ... that's how.