Artists that use the same song structure...

Mumford and Sons, wow, it's like the same song over and over.

Someone once said that every artist or group is just constantly rewriting the same 7 songs over and over again. I agree with that to some extent, but I don't think it's bad, or even necessarily deliberate. It's just that artist's particular pallette of expression. Some artists are a little more limited with their bag of tricks, and some more deliberately experimental.

A few more come to mind - Norah Jones, Alicia Keyes, Enya

Remember when Mick Jagger sang "It's the Singer Not the Song"? When I was younger I strongly disagreed with that sentiment, putting the song way above the singer. Hence my love of The Beach Boys, precisely because they had the best songwriter in the world (Brian Wilson), but only okay singers (except for Mike Love, who was/is dreadfully bad).

As I've gotten older, my thoughts on the matter have changed. And though the song still comes first, singers are of much more interest to me than they used to be. Iris Dement, Emmylou Harris, and Allison Krauss from the gals, John Hiatt, Buddy Miller, and Jim Lauderdale from the guys, being amongst my current favorites.

Pop music songwriting took a giant nosedive in the 70's, when Rock Group's songs became not much more than a guitar riff. The "sound" of a Band became their "song", what they were known for. Bands like Alice in Chains have only one song, really, every single one even having the exact same two-part harmony (and it is not a very good one). Boooring!