There are a few things I don't put smoked paprika in. Spaghetti sauce, for example. Yogurt. Green beans. Chocolate cake. (I use powered ancho for that, ha.)
But seriously, I put it in nearly everything else, so much so that around here it's only worth remarking on what I DON'T put it in. (Me: "So for the chicken meatballs, I used oregano, basil, garlic, capers, and NO smoked paprika.")
Some things I want to taste overtly smoky. Like chili, of course. Or chickpeas and spinach in tomato sauce. In this case, I put in a lot. Two or three tablespoons. My chili recipe is always changing, but the base is generally one part actual powdered chiles, one part cumin, and one part smoked paprika. The smokiness goes so nicely with the beans, and really takes it to the next level.
But more often, it's not about making it taste like smoke. It's about offsetting something else, giving the food a can't-put-my-finger-on-it complexity. Like in a romesco sauce, which is otherwise sweet and peppery. Or lentil soup, thick and rich. Or my favorite feta-and-pepper dip. Or I add just a touch, a teaspoon or less, to a steak rub, or a coffee-maple coating for a pork tenderloin.
Secret ingredient? Secret weapon.