The Ed Sheeran / Marvin Gaye lawsuit going on currently points to a sickness in popular music at the moment.
Over the last couple of decades, money has become increasingly tight in the music business. It's more and more expensive for a label to get a top 5 hit, so even the profits on a successful song aren't a patch on what they were.
Labels becoming more litigious is more likely as profits decrease. You've got to get your money somewhere, and you have to protect your brand. What's more, whereas a suit used to be about a stolen melody, more and more, we're seeing claims about chord sequences. Part of the Sheeran/Gaye lawsuit is the claim that the chord sequence is the same. It'll be interesting when someone tries to claim ownership of the I IV VI V sequence, which has been used in scores, if not hundreds of hits.
Which brings us to playing safe with song writing. Again, because so much is at stake to produce a hit, nobody who seriously tries to make a living from their writing is going to try to be original. It's too much of a gamble. While for the most part, nobody sitting down to write a hit says, "I'll start by stealing part of this other song," they may well start jamming on that trusty I IV VI V sequence.
So we hear chart songs becoming increasingly similar because taking a musical chance is dangerous, and we see more lawsuits as songs rely more and more on their similarity to each other in order to be hits.
Another consequence is that over the course of a generation the average chart listener has heard less and less variety in harmony, and like a child who has only eaten burgers and fries, any new taste / harmony they're subsequently introduced to is treated with deep suspicion.
That's no way to have a hit.
For music that ignores all considerations of chart success, but still wants to be loved, click here.