Huh, my impression is that it was used mostly by the ultra privileged elites. Celebrities, wannabe celebrities, politicians, authors, "journalists", marketing executives, and such. I've never met a regular person that touches Twitter.
My feed has consistently been full of interesting people doing real things, not those you listed with the exception of authors.
Those other places you have to go looking for. If you're on Twitter, and already following some people within your groups, you're likely to see them retweet other people in the group, and over time build out your network that way. I would presume the algorithm will also notice your preference for such accounts, and recommend others, but without personal experience with the Twitter algorithm, that's also just a guess.