This is about declining quality, not increasing diversity (if there's much of the latter).
Today it's mostly cheap gossip (even from major media), rage-inducing pieces, shallow coverage, sponsor ball licking, and "embedded" journalism, that is, exclusives and handouts from the government, the enterprise, and millitary, instead of exposes.
And this goes beyond Scientific American to all media, including those that were already run by and targeted to minorities in the past. It also happened with media in countries without demographic changes, so it's not about whites vs some increased more diverse demographics.
It's the race to the bottom caused by the web, decline of print, rich advertising metrics having them by the balls (not aiming for abstract readers and letting journalists free to write, but being able to micromanage how articles are written to get maximum views).
Newspapers didn't close or go to smaller offices and fire tons of foreign correspondents, staff photographers, and proof editors, for example, "trying to appeal to the widest demographic", but because they couldn't afford them.