It's not so much that it looks childish. The problem for me regarding iOS 7 just looking at sceenshots is that the UI lacks cohesion. Some parts look OK, some look not so good and other areas look bad.I was lucky enough to revert back in time, I don't hate ios7 it just looks childish.
Probably why so many here like it.
Conclusion: apple as we knew it died with SJ. Time to move on.
We are seeing a new Apple these days. Before it was Apple forging ahead and having others copy them. Now it's Apple following trends others have set.