I think this is just partly an inevitable consequence of going from "content scarcity" to our new normal of "content obesity" over the past 20 years or so. In this new era of an overwhelming amount of content, it's just natural to compare it all against each other, e.g. to essentially "optimize" it to the "best" form, but in doing that we've fallen into a homogeneity, and the resulting lack of variation is an actual lowering of quality in and of itself.

2 examples to explain what I mean:

1. I find that nearly all interior design (at least within broad styles) looks basically the same to me now. It's all got that "minimalist, muted tones but with a touch of organic coziness and one or two pops of color" look to it. Honestly, I don't know how interior designers even exist today, when it's trivial to go to Houzz or any of a million websites and say "yes, like this". A while back I was complaining online somewhere that I thought all interior design looked similar where in the past there was much more interesting variation, and somebody insightful replied that it's not really that interior design is now just the same, it's that it's really just converged. People can easily see and compare a million designs against each other, so there is much less of a chance for that green shag carpet to even get a moment in the sun.

2. I was recently on vacation and decided I wanted to read a "classic" book, so I read Hemingway's The Sun Also Rises (I'm not sure why I never had to read that in high school). Nearly throughout the entire book I couldn't help but thinking "Is there any time this book stops sucking?" I hated the entire thing - it was like being forced to watch someone's vacation photos for twelve hours straight, and I kept wondering why there never seemed to be any attempt to actually make me give a shit about any of the characters in the book, as nearly every one of them I found insufferable and wondered how they each had about 3 or 4 livers to spare. But I do understand that Hemingway's writing style was unique and original at the time, and that he was doing something new and interesting that influenced American literature for a long time. But these days, given the flood of content, it feels like most attempts at doing something "new and interesting" are not only forced, but nearly impossible given that there are a million other people also trying to do new and interesting things that now have the means to disseminate them. I don't think a book like The Sun Also Rises, where I believe the main impact was the style of writing/dialogue vs the actual story, could ever break through today.

I guess my point with this long post is that I think the "loss of quality" in content that many of us sense is just a direct result of there being so much content that we see variations from the "ideal" as worse, where in the past we may have found them interesting.