If I remember correctly in my days in Her Majesty's Royal Navy, HMS Ark Royal navigated the Singapore Straights with visual reference to the various brewery signs, Guiness, San Miguel, Tiger etc by triangulation. Must have worked as we never hit anything. Not much in the way of GPS in the 60s.
Perhaps GPS has it's uses but not as the primary system in light GA. How many flight schools worldwide instruct in "glass" a/c from ab-initio? I would guess not a lot.