I always found Kubernetes API reference very useful.

Yeah, that part was always fine, but they sorely lacked a theory of operations -- which is essential for any sort of state machine or orchestrator! -- and basic "man page"-type documentation around processes, config files, etc.

API's and programming languages are indeed very difficult to use effectively without documentation.

They are also not operating system user interfaces, productivity tools, games or web-browsers, and so not the topic of my little sub-thread here.