There's a bit more to exploration than just looking where you want to go and going there. In fact, humans are good explorers precisely for the reason that we can imagine and deduce where to go even if we cannot see it: Most animals are not capable of displacement even if they can sense directions or signals better. You'll also still have access to your hearing and full sense of direction, including wind speed, GPS and satellite imaging. NPCs in the game are affected as well: You haven't really experienced fog without having walked up to a fuling and kicked them dead in the nuts (not sneaking).

Adverse weather exists to change gameplay. You can make camp and/or harvest firewood for future needs no matter your situation, or you can exit the biome and go elsewhere since weather (mostly?) occurs based on biomes, not regions or landmasses.

Temporary fog is fun compared to persistent mist, but we can overcome both.