I think it is probably both. There is separate cultures and groups. And then there is trends. All happening on handful of platforms. Trends can travel between groups when they come big enough. So in that sense it is centralized. On other hand outside trends things can stay inside sub-cultures.

So there is larger centralized culture that reacts to trends like Labubus or Dubai Chocolate. And then there are smaller niche communities that don't really go outside their own.