Saw the same kind of slope in Black Mountain and honestly moss just hid the real problem, which was water pooling because nobody graded the yard right in the first place. Pull the moss back and you find compacted red clay that stays wet for days after a rain, and that is what kills the grass, not the moss itself. Grass needs sun and drainage, so if you have shade and bad dirt, moss is just the symptom that shows up first. Fix the dirt and the slope grade and you can grow fescue there fine, the moss was never the answer.