I would not say "lost its fun", but more diluted, Every new song that gets released makes up a smaller portion of what appeals to a given person out of the entire back catalog.
Back in the 70's you may have had say 100 artists you liked enough to seek out hearing them again each year, Why was that song you listened to as a teenager so Memorable?, because of lack of variety it was played a large amount and had time to cement itself, e.g. You would record it to tape when the radio played it to make up mix tapes, if the radio did not play it so you bought the record, and because they where not cheap you would listen to it multiple times including there B sides, likely more than once.
But now each week a catalog of a similar number of 8/10 or better songs are being released to the average persons taste, so the need to seek out hearing that song again instead of just continuing playing through the service your using is much less
These days you find a handful of 10/10 songs that speak to you every month or so, but it does not mean you will enjoy the rest of the artists releases on the first listen, all this leads to given songs having less impact,
I personally get trapped on those 10/10 songs, usually listening to them on repeat until my mind has understood what hooked it, then they become occasional treats as time goes on.
pop music is popular music, if you don't have enough exposure, then its not really pop,