It’s called a captive market and platform capitalism for a reason. Thanks to the network effect, buyers and sellers gravitate to Amazon. Amazons main product is selling access to it’s walled of market to third party sellers (and attention to advertisers). All of this is to avoid competition and extract monopoly rents. “Ethical consumption” (just telling people not to use Amazon) is fine, but not enough to break this monopoly on its own. It will never work as a single strategy. You also need massive organizing for worker and consumer strikes and/or internationally coordinated state power to forcibly break apart the monopoly.