Every skill list is either incomplete or too generic, sometimes both at the same time. This is especially true for “generic” games meant to be played in a number of different settings. Game designers have to guess about what kind of challenges the PCs will face and how to resolve them mechanically. They usually get it mostly right, but they will miss sometimes.
Navigation is not a challenge that appears in my current fantasy campaign (using Savage Worlds). I don’t ask the players to make a Navigation roll when they are walking through the streets of The City. They just get to their destination (unless I throw in a distraction/encounter along the way). Nor do they have access to explosives, but if they wanted to use the an explosive spell to do something demolition-y, I’d probably use the spellcasting skill.
Genesys is explicitly a rule-of-cool game (which makes it odd that I like it): its Astrocartography is used for things like plotting a better route than the standard one, or deciphering an old star map. It’s caused me to come up with a principle that I think is more generally applicable: only roll the dice if both a success and a failure would lead to something interesting.
I like this advice in principle, but the “something interesting” may just mean that the PCs have to find a different way of solving the challenge. Some game designers fear that failed skill rolls will cause the game/story to hit a brick wall. I say, let the players figure a way over, through, or under the wall.
