Ah, I see your point. Although as musicians, the Black Keys and Nick Waterhouse are primarily concerned with creating new music, insofar as they're interested in creating their music. Sometimes I think of the progression of music as a sort of biological or evolutionary process. Blues is an ancestor of rock and roll, which is an ancestor of rock. Blues is also an ancestor of jazz, which is also an ancestor of rock and roll and of course rock.

The Black Keys and Nick Waterhouse may make music that expresses recessive musical traits, but it's very much modern music. If Nick Waterhouse were to go back to 1955 people might not recognize what he does as being "true" to the music of the day. Others might clearly see the connection, but the difference would likely be apparent to them as well.

The post-modern ideas of how art can be made includes these time travelling moments, that is, the ability to create new works by using elements of prior works. Though the works may be similar or close to works from other eras, the conscious choice in selecting the work's execution shape the intent behind the piece and that's something that defines the contemporary world of the arts.