You want your crumble topping to be on the doughier side. If you find it’s still pretty “dusty” or simply still resembles flour, add more butter.
Your apples should also pile up and ideally be higher than your baking dish. If you use 5-6 apples and they don’t rise higher than the dish, try finding a smaller dish to bake the crumble in or just add more apple.
Walnuts (pecans or cashews work, or hell, use all three you little go getter) make a nice garnish when serving, goes extremely well with chocolate ice cream.