I have been in touch with Tim Berners-Lee and his Solid project since late 2016. Since then, I've run across many people who work at W3C and in the protocol space, and it's inspired me to open up and publish protocols derived from our platform (eg https://github.com/Qbix/auth)
But I believe that, in the end of the day, mass adoption can only be done when there is a popular platform. Whether it's closed source like Facebook or Twitter, or open source like Qbix, it needs to be actually used. That's how, for instance, oAuth came to be so widely adopted, and many others.
Mastodon is used by a million people across a lot of instances and supported ActivityPub before it was a W3C recommendation, so I'd say it is definitely being used.
Adoption and low friction is the most important thing. Unfortunately, copyright makes it illegal to parse web pages without the parent entity's consent, and the CFAA makes it illegal to download them. This means that a low-friction mechanism to break the corporate stranglehold on communication is extremely unlikely, since it can't do much to ease transition between providers.
If we didn't have these restrictions, this would be a purely academic debate, because there are already many practical ways to extract information from a resource and transmit it to other computers.
"Federation protocols" are a way of volunteering this information in a common language, but there's no real technical reason that's necessary to get "decentralized social media" or other such things. They're only considered potential solutions because effective scraping is not allowed.
Decentralized / democratized information access is not an issue that can be solved technically. It needs to be solved socially (primarily because the necessary technical infrastructure already exists, and is just held back by legal anti-solutions).
But I believe that, in the end of the day, mass adoption can only be done when there is a popular platform. Whether it's closed source like Facebook or Twitter, or open source like Qbix, it needs to be actually used. That's how, for instance, oAuth came to be so widely adopted, and many others.
Here is an overview of what I mean: https://vimeo.com/252105786
Protocols like Scuttlebutt or ActivityPub can be bolted on after the actual infrastructure is there.