Heroku is PaaS while AWS started as IaaS and these are completely different. AWS has some PaaS offerings now and is leading the way in an even lighter abstraction with FaaS/serverless. Azure and GCP definitely have unique products but AWS still has plenty of leading tech and I think it's rather misleading to say they don't have anything better. In several instances they're the best simply because there isn't even any serious competition for that niche.

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.