Unfortunately life and economics have no concern about the initial intent of anything, only the current utility.
Systems, at scale, especially when run by biological processes (read: all man-made systems), have a tendency to centralize. Economies of scale dictate that this is just more efficient. We don't have to do anything. The "evolutionary reward" (i.e. your business thrives and moves quickly) of building on AWS far exceeds SPOF issues for small, medium, and most large players. Yes, we get fun references when S3 goes down [1], but it's not as bad as literal water pipes taking down your webservers like what happened with Stats Canada [2].
The fact that Azure and Google Cloud exist maintains a competitive market. I liken it to Darwin vs Linux vs Windows. Optionality, but fundamental components of the cloud.
[1] http://funender.com/wp-content/uploads/2017/03/amazon-aws-is...
[2] https://twitter.com/StatCan_eng/status/873285710094233603