Not an extraneous ingredient in the mix. In fact, I think it could use a pinch of salt and a little lemon juice, at a minimum.
Compare this recipe to apple crisp recipes from Columbiaville, Michigan (an elaborate recipe using corn flakes) and Marshall, Missouri (using cinnamon, oats, and lemon juice).
From a box sold in Canby, Oregon.
Basic Apple Crisp
Slice 3 apples in pie pan.
Mix 1/2 c. flour, 1/2 c. brown sugar, 1/3 cup butter. Pour over apples.
Bake 10 minutes in hot oven. Then 10-15 min. longer.
Yesterdish suggestion: Consider sprinkling 2 Tbsp. lemon juice and 1/2 tsp. salt over the apples.