Floyd mentioned in a previous post that what we hear on the radio today is already old news, the hot writers have already moved on to something else.
I submit that change tends to happen slowly and incrementally. The pattern of borrowing elements from hits of the past appears to have a pretty long shelf life.
What changes is how aggressively one borrows from the past, and which genres are being borrowed from. I'm not very knowledgeable about country music in specific, but I am fairly conversant in the topic of how trends mutate.
I noticed that as I listened to the country station, the older songs borrowed heavily from the 70s, but the newer ones were borrowing from the 80s-90s hits. Some even venture into hip-hop, but that doesn't appear to be main stream yet.
If you look at the demographic, the kids of the 80s and 90s are now adults in the workforce. Many work places have the radio on all day, and advertisers want the radio to be turned to a station that appeals to people in the prime of life spending money on building a life.
Many of those people grew up on 80s music, so it makes sense that young working adults would adapt to new music that contains those elements and influences.