1. File-first paradigm has some valuable properties. One property is apps can't lock data out of each other. So the user can always change which apps they use.
2. Web social app paradigm doesn't have these properties. And we observe the corresponding problems: we're collectively stuck with specific apps. This is because our data lives inside those apps rather than saved somewhere under our control.
3. The question: Is there a way to add properties of the file-first paradigms (data lives outside apps) to web social apps? And if it is indeed possible, does this actually solve the problems we currently have?
The rest of the article explores this (with AT protocol being a candidate solution that attempts to square exactly this problem). I'm claiming that:
1. Yes, it is possible to add file-first paradigm properties to web social apps
2. That is what AT protocol does (by externalizing data and adding mechanisms for aggregation from user-controlled source of truth)
3. Yes, this does solve the original stated problems — we can see in demos from the last section that data doesn't get trapped in apps, and that developers can interoperate with zero coordination. And that it's already happening, it's not some theoretical thing.
I don't understand your proposed alternative with web extension but I suspect you're thinking about solving some other problems than I'm describing.
Overall I agree that I sacrificed some "but why" in this article to focus on "here's how". For a more "but why" article about the same thing, you might be curious to look at https://overreacted.io/open-social/.