I would go on a limb and say that Amazon doesn’t invest in better UX because that’s not what most of their customers care about. Someone at that company has already done the math and decided investing in Amazon Go or 1 hour delivery or Whole Foods is a far better return than investing in UI improvement.

I do think people in this discussion are looking at this from a developer or designer point of view. I read some article a while ago about how Amazon saw a increase in sales from millisecond level improvement in page loads. I bet that’s what they optimize for, and less so on how pretty the UX is.

That all being said, I think Amazon is turning into EBay with all the garbage ads I see on the website, just trying to buy replacement toothbrush heads, but that’s an entirely different discussion.