Preheat the oven to 400° F.In a large skillet, heat the olive oil over high heat. When the oil shimmers, add the ground meat and onion. Cook, breaking up the meat as it cooks until it is browned, about 5 minutes. Add the chili powder, paprika, cumin, garlic powder, red pepper flakes, oregano, and salt. Add 3/4 cup water. Reduce the heat to medium and simmer until the sauce has thickened slightly around the meat, about 10 minutes. Keep warm over low heat. Meanwhile, lay the flour tortillas flat onto 2 baking sheets. Evenly divide the Mexican cheese blend between each tortilla. Sprinkle the Doritos seasoning over the cheese (if desired). Bake 3-5 minutes, until the cheese is melted. Add the hard shells to the center of each tortilla, pressing one side of the shell into the cheese. Bake another 2-3 minutes. Fold the remaining cheesy side onto the hard shell, pressing the shell into the cheese. Spoon the meat evenly into each shell. Top with the spicy ranch, lettuce, and a sprinkle of cheddar cheese. Serve immediately with any amount of desired toppings...avocado, hot sauce, yogurt, cilantro, salsa, whatever you love!