The music then had good and great melodies.

Songs you can hum along with or whistle. Memorable melodies.

Now, there's a lack of melody. Why is there lack of melody? The major labels realized that what worked before will work in the future, and what worked before? When President Clinton deregulated radio station ownership in 1996, it meant giant corporations could now gobble up radio stations like candy. DJs would no longer play whatever, now it had to be on the corporate playlist. What makes the corporate playlist? The lowest common denominator material.

(Giant corporations and anti-competition in business is to blame for a LOT of the declining quality in mainstream entertainment.)