One of the biggest benefits of Amazon IMO is it's homogeny. That is, It's ability to let you buy products from dozens of different categories, among thousands of vendors, with a unified shopping experience. For any competitor to replicate this would be a monumental task and it would probably take years to see profit. I think most of us want to see decentralization of retail and increased competition and the best way might be a decentralized shopping platform.

While not something that can easily be shoehorned into the Fediverse I think it's worth the effort to try. Sensitive info like addresses, order history, and payments would still have to be managed outside of the Fediverse, but I think it is feasible to have a federated platform that makes it easier to connect consumers with retailers.