Let's flip your argument on its head.
If Amazon only had three customers, would they be enabling wasteful consumerism? If so, why? If so, wouldn't literally every online or offline marketplace be enabling wasteful consumerism?
If not, why? How many customers / year need to visit before they become the monster you claim? Or is it a gradient? If so, then what is their responsibility - to only let a certain threshold of people purchase goods every year, and turn the rest of consumers away?