Given that I'm in this business, I'm something of an outlier, but I find it more appealing to hear either music before those prime years typically considered the ones where one's taste primarily develops and that I am supposed to have nostalgia for or new music.
For instance, classic KROQ (pre-grunge) or current KCRW is far more interesting to me than either 98.7 or 106.7 in Los Angeles. A part of it is, I suppose, being heavily interested in radio and as radio became more consolidated, playlists did become more conservative and uniform, and over time, alternative for instance crossed over to pop, became more "new rock" oriented, and there was also Modern AC which had a fairly short playlist and shared a lot of those tracks.
To me, 80s music and even 70s is still refreshing when I'm in the mood for it, or I'll sample an independent or non-commercial station and hear something new. So when I'm listening to classic hits radio, hearing stuff from the years where supposedly I'd "fondly" remember those songs, for the most part doesn't. It wasn't an era of my life I have great nostalgia for outside of music, so it doesn't evoke much in me that's positive, and I've heard the songs so much that even the ones I like I only need to hear very occasionally.
I say none of this to suggest I'm a typical listener. Merely to suggest that a factor may be that music from earlier eras holds on longer because it can evoke positive response in a wider range of demographics in a way later more polarized songs don't.
Your point about "polarized songs" jogged a memory with me. Several of the songs I like now--including The Grass Roots' "Sooner or Later,"--I didn't like when they were popular back when they were hits (in this case, in 1971). I tuned the songs out because they were being overplayed and I couldn't stand to hear them anymore. Fast forward to the 2010s, and I find that I can hear many of these songs again--radio, including Internet radio, is playing them a lot less and I find that I don't feel so "polarized" about listening to them as I once did.
