The selection in these channels was the tribe back then. They were the "bottleneck" of pop culture.
From around 2000 with broadband etc, "payola" (broadcasters being coerced by record companies to play their flagship songs "in heavy rotation") is less and less effective.
As a consequence, I think the "current fashion" of music seems less defined.
I don't miss the restrictiveness of a single culture and the expectation to fit into it, but with the benefit of hindsight I can't say it was a terrible culture, given all it had to do.
The sort of people you found at, say, a metal show in the 80s and the sort of people you found at a dance club playing the early era of house music were wildly different. Even if you keep it within rock, the overlap of the audience seeing The Cure would be wildly different from those seeing Judas Priest.
Anime? Even before the internet became what it is today, you could go to a comic book store and hang out. There was significant overlap between the comic book/dungeons & dragons/anime crowds.
There have been social spaces and places to meet people within specific cultures for forever.
I was into D&D, so I was exposed to anime, comics, Monty Python, Mel Brooks, and Tom Lehrer, because those were a certain subculture.
I was never a comic-book nerd, but I could probably name a dozen different series from image comics in the 90s because I was surrounded by people who read them.
I flat out dislike watching Mel Brooks movies, but I can quote about 90% of Spaceballs or Blazing Saddles because that was a part of the vocabulary of that group.
Mainstream always coexisted wirh smaller cultures.