And then we go back to processes, System V-like IPC (shmget()/semget()/msgget()), and network configuration subsystem (routing, firewall, bringing interfaces up or down, and the like; netlink is only a recent development, after 2000).
What was it about the mantra again?
Well, the mantra is of course an aspiration. In practice things are not always done that way, especially in the past. SysV ipc is hopefully a thing of the past though.