This was a really good article, thank you for sharing / writing it.
ActivityPub and Mastadon do have some pretty strong architectural benefits, but the challenges we face in making the Web federated again is, as it always has been, social, not technical.
One of the things that was a bit of a dirty secret outside of Silicon Valley for a long time was that the organic growth that various platforms touted, largely wasn't. Teams of people would pay media personalities and businesses to use their platforms in order to get it into the public eye.
This to me is the main issue the fediverse faces. The issue remains adoption. Even the UI's of mastodon and some other fediverse services have surpassed the big tech offerings in speed, usability, and easiness to use.
But no matter how many more features we offer, the fediverse could stay at a stagnant <1% of total social media users, unless it tackles the problem of effective adoption and onboarding.
It's also complicated by factors mentioned in the article, having to do with incentive structures. Most open source projects stand against the "viral growth" model that tries to grow its userbase at all costs, where each new user is seen as a potential income stream. For people running servers, new users mean more work, for no gain. As the writer mentioned, these social media startups employed teams of people dedicated solely to the task of growing their userbase, getting media attention, and spreading awareness. Open source projects rarely have the resources to do that labor.