IOW, why would music that is intentionally written to peak in the top 10, require to be musically diverse or innovative? Marketing the artist, or creating PR 'buzz' in the press seems to be more important than how many scales or time signatures an artist can play.
Of course it doesn't require it, but it's a nice feature.
One feature of good music is that it can surprise the listener (key changes, chord changes, sudden shifts in rhythm or even style).
musical skill has been devalued in the top 40 for decades.
It's just when you turn on the radio, it all sounds the same.
The promotion machine makes it such that the music put in front of us all tends to sound the same, because the industry is just trying to rehash the same hit over and over to milk us for money.