> AWS is just late to the game because they've rolled so much of their own stack instead of adapting open source solutions and contributing back to them.

This is emphatically not true. Contributing to KVM and the kernel (which AWS does anyway) would not have accelerated the availability.

EC2 is not just a data center with commodity equipment. They have customer demands for security and performance that far exceed what one can build with a pile of OSS, to the extent that they build their own compute and networking hardware. They even have CPU and other hardware SKUs not available to the general public.