Sauce: Pulse all the sauce ingredients in a food processor or blender until mostly smooth. Add water if needed to thin.
Slaw: Toss some of the sauce (not all) with the cabbage. Reserve the leftover sauce to top the tacos.
Shrimp: Pat the shrimp dry with paper towels. Toss the shrimp in a small bowl with the spice mix to coat. Heat a drizzle of oil in a large skillet over medium-high heat. Add the shrimp and sauté for 5–8 minutes, flipping occasionally, until cooked through.
Assembly: Layer each tortilla with smashed avocado, slaw, and shrimp. Finish with Cotija cheese, lime wedges, and extra sauce.