This is interesting. Putting aside AWS, Amazon has for a long time been a logistics company at it's core - the website is terrible from a customer perspective, pricing isn't great and the seller/supplier experience is certainly weighted in Amazon's favour. What they have is the critical mass of customers who are invested in prime and it's the default choice. I hate them but if I need something quick I generally hold my nose and ask my wife to order on her account. Other sellers can achieve delivery just as quick, it's just inconsistent between sites.

As someone who builds ecommerce sites and has seen Amazon become dominant I've thought about how to solve this problem many times - it requires deep pockets and most importantly good logistics. I've often thought if a logistics company expanded their shopping cart plugins to also (optionally) feed back data to a central ordering system and included their own payment solution to allow direct from customer ordering with centralised ordering, payment and logistics - perhaps at a loss until a prime type offering could be built there would be a potential for a strong business. Amazon take a huge amount of fees a chunk of which go to putting the wrong product in front of the customer!