What does that have to do with Cory’s concerns? They don’t want to build an audience on Bluesky because that promotes Bluesky, a dangerous place to build up, in the view given by the article. It would be neglectful to let it gain enough power to become a Twitter 2.0, we have an opportunity to prevent us repeating history.
The easiest way would be to quickly look up the ones you don’t know yet. Many have Wikipedia pages and the others usually have good home pages explaining what they do. But as you can see, there’s a wide range for hosting different kinds of media and discussions.