Anecdotally, Canada & US Amazon used to be like you described when they first started becoming the "everything" store but things have really declined lately.
6 or 7 years ago there was a much higher proportion of items actually sold by Amazon. Now it's a morass of third-party sellers with inaccurate listings to the point that even just finding an item is quite a choice. I recently gave up trying to buy kitchen knives because most listings had no OEM part number, a vague description and photo and people arguing in the Q&A section about basic features like whether it had a serrated edge or not.
Amazon has become a dumping ground for people who buy things on Alibaba, at liquidation or even just at Costco and try to resell for a markup. Even a search for basic consumer products like a box of cereal will have the top results be these kinds of sellers. For instance, I just searched for "ichiban noodles" (a popular international brand of instant noodles that can be found for Yes, Amazon still replaces or refunds almost anything that you have an issue with, but I'd rather just get the thing I wanted the first time.
A perfect of example of this is a picture frame I bought from Amazon (or rather, third party seller fulfilled by Amazon). It arrived damaged because it was thrown into a too-large box with no padding. I notified Amazon and they sent another one. It arrived identically packaged and also damaged. Then I asked for a refund. At this point, almost a month had passed and I still didn't have a picture frame, despite a huge amount of resources having been consumed by Amazon.
No store that actually has to bear the cost of returns themselves would do that, but Amazon made out like kings on the transaction: they got a cut of the original purchase, their FBA fees, then got to charge the seller for disposal of a broken item - twice!