No, federated model is chosen over distributed model or centralized model to allow feuds, putting it simply.

That may work for a Reddit alternative, but doesn't work for markets. Helps moderation (some idea of it, I don't think that idea is good), but definitely hurts a single space to sell and buy stuff.

Which is why cryptobros and such types make either centralized or distributed systems.

So much for using computer networks for this.

Now about Amazon specifically - your post omits the whole warehouses and logistics part. Which is most of Amazon's core business.

Computer people today somehow started forgetting that real life is very hard and complex. When I was a kid (born 1996, so not old man), computers had a promise of making that real life easier, and from time to time delivered on it, but at some point bullshit like glossy buttons and Web 2.0 and social media became a thing in itself, and everyone started behaving as if it's done, we now can look down like olympic gods to those mortals messing around in dirt, and sometimes easily solve their problems. We can't.

Getting back to logistics - one has to design a system of shared warehouses, transportation, mailing and delivery tasks, tracking, reporting on outcomes of every event, and all that should be even more abuse-resilient than the processes inside actual Amazon. You'll have Byzantine problems in every interaction.

The "distributed king of all social media, solving once and for all the problem of centralized platforms" that I'm often dreaming about is realistic compared to that.