this is true, but a lot of resources put into a new team that was completely walled off from the rest of the company, in terms of roadmaps and eng culture, could overcome this problem.
I think someone at Amazon in the mid-2000s would not have necessarily looked at their internal stack vs. other companies and picked them to become the breakout cloud winner, but when I was there (late 2000s), the AWS team was kept quite separate, and aside from things like S3 the retail side of the company wasn't really using much in the way of AWS infrastructure yet.
Amazon starting a cloud offering is quite different from anyone coming later. Even though lot of open source infra exists, expectations from dev/companies in 2015+ are sky high. If FB really wanted to have an offering, it needs to be specialized in something specific. May be Oculus game server hosting or something tied to FB/WhatsApp/Insta features
I think someone at Amazon in the mid-2000s would not have necessarily looked at their internal stack vs. other companies and picked them to become the breakout cloud winner, but when I was there (late 2000s), the AWS team was kept quite separate, and aside from things like S3 the retail side of the company wasn't really using much in the way of AWS infrastructure yet.