There's a lot more fragmentation.
The few common grounds, the most popular music, 'content creators', ideas and current events get amplified by news sites relying on ads, algorithms seeking maximum engagement.
It's hard to promote a fringe issue in a wide content channel and there's a lack of everything in between fringe and mainstream.
Yeah sure, but saying that there are no "dark corners" is just naive. Counterculture in the 70s or 90s weren't massive movements at all. I don't see how it has changed looking at teens at the school of my children. It's mostly the problem of getting older can centering more with the mainstream yourself.
It's hard to promote a fringe issue in a wide content channel and there's a lack of everything in between fringe and mainstream.