Amazon entered Day 2 as while back. Its customer service has been a shadow of its former self for years now. It also took them years to resolve the problems stemming from commingling their inventory with 3rd parties.
Are those co-mingling issues actually resolved now? I still avoid purchasing anything on Amazon where receiving a counterfeit or slightly not-as-described item would be consequential. I haven't personally had a bad experience, but have read enough anecdotes and reviews about it over the past year or two that it has strongly shaped my Amazon purchasing habits.
I have lost faith in Amazon a while ago. I base my opinion on their amazon.com online shopping experience. The ratings are regularly gamed, the "Amazon's Choice" label is completely unreliable, the quality of products sold by Amazon under their own brand (Amazon Basics) is highly suspect, they're not price competitive any more, I won't buy baby or health care products due to poor warehousing practices and commingled inventory. Several years ago shopping at amazon.com meant you'd likely get a price competitive, good quality product with reliable reviews. Sadly that situation doesn't exist any more.
From what I read on HN, its customer service must be very variable regionally. In the UK, I often knowingly pay more to buy from Amazon, because it continues to be my experience that if something goes wrong or isn't up to scratch, worst case they'll refund and send Hermes to collect it, no questions asked.
Also Audible, a subsidiary of Amazon, has very good customer service and a notoriously generous return policy. So it veries depending on business group as well as region.