Rock music has depth. Songs are emotional, passionate, they come from the soul of the songwriter...which in rock music, usually means the band themselves. That's how country used to be. Johnny Cash, Hank Williams, John Denver...they all wrote their own songs. Which gave life to the "story telling" in country music. There was a lot of respect for that.
When you flip over the liner notes to your favorite rock album, you'll see the names of the songwriters, which you can quickly identify as band members (and sometimes the producer). When you look at a pop album, from Katy Perry or Rihanna, you'll find anywhere from 5 to 15 "songwriters". Mr. Cash is sometimes remembered as a ROCK icon, his legacy shares more with modern rock music than modern country. The current state of country music shares more with the pop music world. An environment where you don't know if a Taylor Swift or Carrie Underwood song is "country enough". These songs end up with 5 to 15 writers on them...unlike rock artists.
Which brings me to the proof part. How can you prove that country music has regressed to a basic formula? Can I prove that not only do they use the same concept over and over, but the same words and phrases? Well, I don't have to...because someone already did. Here is 2013 in country music: