It is missing one crucial truth that dispels the thesis: The fact that a social network does not need to be owned by one entity for everyone on it to be able to interact with each other. See Federation[0], federated social networks like Mastodon[1], PeerTube[2], Pleroma: where you have an account on a Mastodon "instance" (computer), but you can talk to anyone speaking the same protocol, ActivityPub[3]. A Mastodon account can follow PeerTube accounts and Pleroma accounts. And no one controls all Mastodon servers, your Mastodon server is controlled by your server administrator.
The author does not seem to understand the internet fundamentally.
Email is an example of a federated communications protocol.
[0]: https://fediverse.party/
[1]: https://joinmastodon.org/
[2]: https://joinpeertube.org/
[3]: https://www.w3.org/TR/activitypub/
The next question: should we force Facebook, Twitter, Instagram etc. to submit their platforms to open protocols the same way Mastodon is?
Maybe the answer isn't getting everyone to use Mastodon; maybe it's using anti-trust law to force the big centralized companies to operate more like parts of a federated system.