OK, here's the problem in a nutshell: no one among regular people cares. You guys are splitting hairs right now when talking about the difference between tweeting and boosting or public companies vs open source or what have you. None of that attracts users. If you have no users, then for regular people, your product is useless. Even the article is not really making a pitch for mastodon that indicates any features at…
I think you nailed the USP of Mastodon. Keeping out the marketers, advertisers, vanity metric chasing or fandom makes Mastodon that peaceful scenic beach where your fellow beach goers say hello and share some of their food with you. I'll take Mastodon fringe over obnoxious Twitter or Facebook anytime.
The idea of "mainstream" is dying, and will continue to do so. What we're seeing is a deep cultural fracture where communities, ideas, and people do not form the kind of stardom or centralized propagation of ideas that the previous decades were known by. As production gets cheaper, and getting an audience becomes easier, people will begin to form seamless self-sustained communities that support each other (think patreon).
If video killed the radio star, then the internet killed the star, and fractured it into infinite pieces.