> There's a reason why most FAANGs developed their own packages management and deployment system and keep using them. They are simpler, less bloated, easier to debug.

Most FAANGs developed their computing infrastructure before Kubernetes gained popularity. After all the investment into building it and fine tuning for their software services (like ads), they probably have a lot more reasons to not migrate to something different. Not just because their systems are "simpler, less bloated, easier to debug".