I think the "homogenization" is the keyword here. It's not that trends are bad, it's just that, in the 'old days' a trend might start as a community-wide phenomena that over time might spread into neighboring communities, finally becoming part of the local / regional zeitgeist.

These trends would spread slowly enough that other trends in other communities would have time and room to grow and develop. The result is you get a bunch of localized cultures, all unique in some way.

The best analogy I can think of is a plant mono-crop. Instead of different species of plant gradually finding their niche, we plant 50,000 acres with corn or soy.

I have to say, even over the last 20+ years or so, it really does feel like you can go anywhere in the world and get a very similar experience. You can go to the local 7-11, buy a coca-cola, hit up your local costco, listen to people arguing about American politics. It just feels like different countries have gradually been losing their unique culture, and we just have this global homogenized version with slight regional differences.