Many people I am sure have realized the need for such a thing for many years. You can include me in the list of such people.
I am co-founder of a startup producing an ECM product. The product is, amongst other things, designed to be able to address the need you are pointing out. The company is named 'Carbon State' and the website can be seen here: https://carbonstate.com
What is needed to be able to have an "Amazon style shopping experience" is a site that can easily allow anyone to list any known object that could be sold in a cleanly organized way. This requires many different things:
1. A system that can scale to enterprise levels ( meaning many servers working together but appearing to be a single website to the user )
2. A hierarchical tree of categories in which items are located, that can easily be updated by many different groups simultaneously and audited for accuracy.
3. The ability to allow multiple structured definitions of products at any point on the tree. That is, the ability to define what constitutes 'a thing that can be sold' at that point in the tree. Different types of things with different sets of attributes could be at each point in the tree.
4. The ability to let product owners define visual layout for their products in an appealing fashion that is compatible with all users of the system. ( and the ability to prevent them from messing up the large system by doing this )
5. The ability to let individual shop owners control their payment process entirely, while still allowing a 'global payment gateway' to exist. This essentially means that different stores will have their own websites as well, but they will feed in a clean structured way into the global system.
6. A system that does not charge any percentage of the value of the products on sale, and charges a very minimal fee for businesses to join the global gateway.
The product my company is working on will, when complete, address all of these needs.