I think their biggest weakness is their relationship with sellers. Sellers hate Amazon because their livelihood is dependent of Amazon's ever changing policies

I think their biggest weakness is their relationship with sellers. Sellers hate Amazon because their livelihood is dependent of Amazon's ever changing policies and bans. This is why most of them have a Shopify store and hope to create a brand on their own. But, they haven't succeeded yet. If you can provide a credible alternative for these sellers, there will be a stampede of sellers out of Amazon.