It's important to note that different platforms require completely different approaches, since they work in different ways.
For example. The text focuses on Twitter, a microblogging platform; in microblogging a few people get a disproportionate large amount of followers, while most others are simply following those. That enables you to identify "key players", as the text calls them; and if you migrate them, the rest will follow.
Well, that would not work to encourage people to ditch Facebook. In FB you don't really care about a handful of "influencers"; you want news about your friends and family. You're better off convincing clusters of highly connected people to migrate instead.
Then there's Reddit; network effect still applies there, but indirectly - you don't care about the people themselves, you care about the content that they provide (as either links or OC). To encourage people to migrate off Reddit you need to provide a substantial amount of content in your alternative. (That's basically what we [users] have been doing in PieFed/Lemmy/Mbin.)