100% with you on every point. It's the only language I've worked in that lets me read other codebases without an hour or two of "wut?" happening, so they did something right!
Yes, I find the K8s codebase pretty easy to read actually, but I am biased since I work with K8s and the codebase makes a lot of sense when you understand what everything does already.
Kubernetes is a behemoth, but the Docker (Moby) source code is actually pretty easy to get into (if you're already a Docker user and understand how containers work)
The point is in Go it's pretty hard to write code so ugly that it'll be hard to read. I'm actually quite confident I could quickly onboard on almost any Go codebase (Kubernetes might be an exception). When I used to work with Java, I very rarely even tried to read the source code of my dependencies because it was unreadable.