This is our hand-drawn map of our immersive-mode Valheim map - I sail while my partner maps on the boat. We call out terrain observations, bearing, etc while we're sailing.
Currently, we're settled on a Plains island in the south, four days' sail from spawn, and have established a full base in preparation for Ashlands.
Speaking personally? Not at all. It's just an additional fun thing to do. You could probably manage without it by memorizing routes and making land markers as well (which we do).
If anything (she says), it makes it MORE immersive, because then you're engaging with the terrain and paying more attention. Plus, it gives her something to do on the boat.
They really should add something for passengers to do. Rowing. A crow's nest with a higher render distance or for shooting arrows.