I am pretty sure someone posted here:
"Most modern day orchestras are nothing more than 1700's-1800's cover bands!"
But yes, music does evolve.
US country music 1950's is very different from 2010's country music. Does that make one country music and the other not country music? Ummmm, probably not.
For most people (of course not every one), the ages from maybe 10-30 set your musical tastes and personal understanding of what a certain "genre" if music should sound like.