For as "terrible of a language" Go is alleged to be for a container runtime, its not like crun or youki are exactly faster in many meaningful ways unless you count churning containers running true and exiting.
And implying the system kernel still has to run the container kinda ignores kata containers and gvisor runtimes.
For me it's not about the cpu time, but the memory. If you spin up hundreds of containers the docker overhead becomes very real.
It's about using go to develop container runtime being terrible and not that "if it was C it would be faster". OS runs the container, docker just does the setup and some managmenent.