Not to offend you or your work, but IMO Amazon makes the worst software out of all the big tech companies. I think that this is related to their ability to attract and retain talent due to their poor work culture.
walmart.com is better designed that amazon.com. I don't know when that happened but you can take a look at two product pages for the same book and be the judge. [1][2]
That's just the tip of the iceberg. I could rant about Amazon's software for days, but in the end software doesn't necessarily mean they are a bad company. If I order something from amazon I expect to get it quickly and in the case something goes wrong I can talk with someone who will be more than agreeable. That is why they are successful, not because of their software prowess.
[1]: https://www.amazon.com/Thinking-Fast-Slow-Daniel-Kahneman/dp...
[2]: https://www.walmart.com/ip/Thinking-Fast-and-Slow/20530246
Walmart can do one thing right, while Amazon has the majority of it right for me. It's going to take a lot to sway me away from Amazon.
I'd also say that if AWS had a 6-7 year head start on the competition, then that was the competition being lazy. It's not as if Microsoft/Google didn't have the ability to deliver a cloud platform back in 2007, and history shows they were delivering cloud products around this time. Microsoft Azure was announced in 2008 and launched in 2010; Google App Engine launched in 2008, storage in 2010, and VMs in 2013.
The design of a webpage for companies doing 100s of billions in revenue will be rather subjective and hard to change without materially affecting that revenue so I'm not sure how valid that comparison really is, or what it has to do with "better software".
I will say that building the infrastructure to power such an efficient ecommerce empire along with AWS is not trivial and you're likely vastly underestimating the quality of their systems based on what seem to be rather surface-level observations.