The big issue with Amazon isn't customer service within the return window, but rather counterfeit goods and misrepresentation of products from third party sellers. There are a disturbing number of outright dangerous products being sold on Amazon and very little accountability. It is a big enough problem that it was named as a risk to their investors in a SEC filing from 2018.
There is a difference here that makes it easier for Amazon to sidestep responsibility: Most of these products come from third party sellers. This gives them a way out, and it is tough to fight because they have deep pockets so who is going to go after them?
If a fake oil filter from Amazon blows an engine, the overseas seller isn't going to do squat and good luck getting anything from Amazon.