In 2012, Spanish scientists ran a study that compared about 500,000 songs over fifty-five years of what broadly be called popular music. What they found was that, over time, music has become more and more homogenous. Which shouldn't be surprising -- even to casual listeners, it seems apparent that vocalists have begun to sound more and more alike. There's a really weird pseudo-Estonian affectation among female pop vocalists where they kinda slur together multiple vowel sounds and needlessly add '-ow' phonemes. In the last few years there began a phenomenon in which singers would pronounce 'love' so that it rhymed with 'stove,' and what happened next? (COVID-19, just asking questions.)
It's not just vocal quirks that are becoming more same-y, of course: the music itself is becoming more simplistic (and louder, in the hopes that you won't notice). Maybe you've noticed things like the mistakenly-named millennial whoop. (I say mistakenly-named because the real millennial whoop already exists; it's the sound we make when we get hit by a bus and we realize the insurance payout will alleviate ten percent of our student debt.) The millennial whoop is one of those things that, once you've noticed, you'll hear everywhere, like the Scotch Snap, or the Triplet Flow, or the Amen Break. Whether you think these things are passing fads or not, ultimately it's true that ultra huge pop music has steadily been becoming more and more similar. But the question is, why?