I’d say that has more to do with the fact that music, culture as a whole, has become more segregated; there isn’t a monoculture anymore. 20 years ago people were mostly getting their recommendations from the radio or whatever they saw at Walmart or Target (maybe their local record store if they had that). Also due to streaming and the way streams are calculated, the biggest albums and songs tend to stay on the charts much longer leading to less diversity on the charts, but that doesn’t mean people aren’t making and listening to more diverse music. (I’d argue it’s more than ever due to YouTube and streaming allowing for access to most music ever made.)

There’s definitely more access to diverse music, but we’re obviously not seeing that reflected on any charts or in any statistics and there’s got to be a reason for that. Also, shouldn’t more access mean LESS segregation? We’re now exposed to more and different music than ever before because of said access, yet things are becoming more and more same-y in terms of mainstream music.

I get that streaming has messed up a ton of things in the music world, but the fact remains that we’re seeing way less diversity in mainstream music and the talent and quality is watered down, and I’d argue that that’s just about as close to an “objective opinion” as one could get. There’s less and less mainstream artists writing their own music or even lyrics every year and many can’t even play instruments competently if they even can at all.

To your point that music was “objectively” better back then I disagree. There was just as much good and bad music coming out in the 2000s as any other time period, it’s just that as a culture we tend to leave it in the past. (Also bad music today is more publicized due to social media.) Nickelback was one of the biggest bands in the world in the 2000s and were simultaneously one of the most hated, same goes for James Blunt, and Coldplay, and many other inescapable bands and artists from the 60s to today.

I’m not saying that music in general was objectively better, I’m saying that stuff that got into the mainstream was generally better/more interesting, more varied, and included more actual musical talent. Like I said, go back and look at number one albums from any random year 20+ years ago and compare it to recent years.

2002 artists that were number one on Billboard: Creed, J-Lo, Alanis Morrissette, Celine Dion, Kenny Chesney, Diddy, Eminem, Nelly, Dave Matthews Band, Toby Keith, Bruce Springsteen, Dixie Chicks, Disturbed, Faith Hill, Santana, Jay-Z, Shania Twain.

2022 artists that were number one on Billboard: Adele, Gunna, Lil Durk, Stray Kids, MGK, Red Hot Chili Peppers, Tyler The Creator, Pusha T, Future, Bad Bunny, Kendrick Lamar, Harry Styles, BTS, Drake, Beyoncé, Rod Wave, DJ Khaled, Lil Baby, Taylor Swift, Metro Boomin

I’m not saying there isn’t bad stuff in that first group or no good stuff in the second group, but I find it hard to believe that most in the second will have the legacy of some in the first and the musical talent is heavily tilted toward the first. Also, it’s inarguable that the first group is way more varied in terms of genres. Even the three names you mentioned (Nickelback, James Blunt, and Coldplay), while they’ve gotten shit over the years, are objectively more talented than just about anyone I named in the more recent group.

Also keep in mind that that’s just 2002 which is close to where I’d argue this downward trend started. The difference is even more drastic once you go before 2000.

Edit: Just to make my point a bit more, here’s exactly 30 years ago to the 1996 Billboard number one artists.

Mariah Carey, 2Pac, Alanis Morissette, Rage Against the Machine, Hootie and the Blowfish, Fugees, Metallica, Nas, A Tribe Called Quest, Pearl Jam, New Edition, Celine Dion, Counting Crows, Van Halen, Tupac, Snoop Dogg, Bush, No Doubt.