Amazon owns one of the most sophisticated logistics networks in the world. They own warehouses and robots and trucks and planes. All of that adds up to a meaningful, valuable contribution to the world.
I buy tons of stuff on Amazon. I buy from them rather than from eBay or an independent online retailer because I know it'll actually get delivered to my house on time. For me, the marketplace is basically irrelevant - it's the promise of fulfilment by Amazon that I care about.
I sometimes reluctantly buy from an eBay seller or a random e-commerce site when the item I want isn't available on Amazon. Those retailers tend to offer "FREE DELIVERY", but they also tend to be very evasive about how long it'll take and which company will do the delivering. Sometimes they'll advertise next-day delivery, but take two or three days to actually dispatch the package. Sometimes they'll use an ultra-cheap delivery service that takes 3-5 days, with no prior warning of which day they'll actually try to deliver on. Sometimes their terrible delivery service will decide that they just can't be bothered to deliver to my house, so they'll lie about having tried to deliver it and tell me to collect it from a warehouse. Sometimes they deliver to somewhere random in the vague vicinity of my house (a neighbour, underneath a parked car, behind a bush) and I get to play a fun scavenger hunt where the prize is something I already paid for. These bad outcomes literally never happen to me when I buy from Amazon.
In the event that something did go wrong with a delivery, I'm confident that I could just contact Amazon and they'd make it right; when something goes wrong with $OnlineRetailer, I often find myself refereeing a dispute between the retailer and the logistics company, both of whom deny responsibility.
There are plenty of alternatives to Amazon, but from a customer's perspective they just suck.
All of what you're saying has to do with Amazon fulfillment (FBA), not Amazon.com the Internet marketplace.
They're two entirely different things (you can actually use Amazon fulfillment for items sold on other websites, although it's typically too expensive). If Amazon fulfillment continues to dominate on an independent platform, that's great, they earned it, but at least they won't have absolute pricing power because sellers will have alternatives, and at least other companies will have a chance to impress you, too.
I'd figure that the marketplace would show the fulfillment company in addition to the way that the courier is typically indicated, so that customers could express their preferences. If the item does a lot of volume, perhaps a seller would even have inventory with multiple fulfillment companies, and buyers could pay a surcharge to get their preferred fulfillment, same as shipping.
I buy tons of stuff on Amazon. I buy from them rather than from eBay or an independent online retailer because I know it'll actually get delivered to my house on time. For me, the marketplace is basically irrelevant - it's the promise of fulfilment by Amazon that I care about.
I sometimes reluctantly buy from an eBay seller or a random e-commerce site when the item I want isn't available on Amazon. Those retailers tend to offer "FREE DELIVERY", but they also tend to be very evasive about how long it'll take and which company will do the delivering. Sometimes they'll advertise next-day delivery, but take two or three days to actually dispatch the package. Sometimes they'll use an ultra-cheap delivery service that takes 3-5 days, with no prior warning of which day they'll actually try to deliver on. Sometimes their terrible delivery service will decide that they just can't be bothered to deliver to my house, so they'll lie about having tried to deliver it and tell me to collect it from a warehouse. Sometimes they deliver to somewhere random in the vague vicinity of my house (a neighbour, underneath a parked car, behind a bush) and I get to play a fun scavenger hunt where the prize is something I already paid for. These bad outcomes literally never happen to me when I buy from Amazon.
In the event that something did go wrong with a delivery, I'm confident that I could just contact Amazon and they'd make it right; when something goes wrong with $OnlineRetailer, I often find myself refereeing a dispute between the retailer and the logistics company, both of whom deny responsibility.
There are plenty of alternatives to Amazon, but from a customer's perspective they just suck.