Is a compass really needed on the AT? On most of it these days...maybe not. It's so well traveled & marked. Do I bring one, yes!! With a map. It gives me the chance to become unteathered. Freedom to explore more.
Living at a hostel for a season I enjoyed meeting many thru hikers. I did mine back in 88 & did have to use my compass several times. Times & methods have changed. Even when I mentioned 5-7 day resupplies on PCT to a few they said it wasn't doable. There were times on it that I was lucky if I saw trail twice a day navigating by map & compass due to high snow year.
If you want to limit yourself to hiking blaze by blaze, go for it. If you want to cut the teather & hit real wilderness, learn map & compass. Explore country not limited by batterie life.