You call that dumb?
What you used is actually a heuristics path-finding algorithm. The only difference between yours and those found today is that you created higher heuristic level (nav-zones) manually while in todays heuristic path-finding algorithms these higher heuristics levers are created automatically using various algorithms.
So don't call your path-finding algorithm dumb mechanics because it is quite advanced path-finding algorithm.

Now you might think: But wait it seems so easy to understand.
Of course it is easy to understand. Why? Because you are using it every day in your life.