They didn't have to bring anything back. Not everyone agrees ID Crisis was a bad thing. Many, like me, found it to be the best JLA story of all time.
But we don't need to agree about that. That's what's so wonderful about what seems to be happening here. It seems like we're getting it ALL back, which isn't just a New 52 correction; it's a correction of DC's original sin, Crisis on Infinite Earths... The first time the DCU was retconned to the exclusion of old stories and the first time we were told any story 'didn't happen.'
This is what I've been wishing for from DC Comics since 1985. It's been a long wait but I'm so pleased that the DCU's entire, rich history has been restored. And it really seems like that's what they're doing here. I can't imagine anyone being unhappy about that. And, when it comes to comics fans, everything seems to make somebody furious. I can't imagine this doing that.