I think for me the problem with Bookwyrm (and one of the reasons I'm not really looking to move from Storygraph) is that I don't really see services like Goodreads or Storygraph as social networks. I'm more interested in being able to manage lists, recommendations, progress, etc than I am with interacting with users on those platforms. I think they're so specialized, that federating with those types of apps to Lemmy would end up a lot of noise on both that wouldn't really make sense for either.
The only thing I can see making sense for federation for me is maybe being able to follow a reviewer I like via my Mastdon account, so I can keep track of reviews without having to log into the platform.
That's just my thoughts though, but full scale federation vs something more like RSS to me is where the line between social network and app with social features lies for me.
Using the iMessage analogy, we're currently in a state where green bubbles can't interact with blue bubbles at all. Nobody should be expecting full interop with a corporate platform, but for the long run I'd rather have partial interop at arms length.
Embrace extend extinguish only applies if platform is so focused that it cannot sustain itself without the extend phase, and the extend phase cannot happen without something to embrace.
People aren't seeing the forest for the trees here. Yeah, nobody likes Meta, but the larger impact of Bill C18 will be that sources like Google and other large aggregators will stop allowing links to legitimate news sources, and instead be flooded by blogspam and misinformation.
People won't suddenly be navigating to The Toronto Star when they don't get news on the latest updates in say the Corona virus in their immediate Google results, they'll just continue to click on through to whatever sketchy source manages to SEO their way to the top instead.