Pat the tilapia fillets dry and coat both sides evenly with the blackening seasoning.
Heat the olive oil in a large skillet over medium-high heat until it shimmers.
Place the seasoned fillets in the skillet and cook for 3 to 4 minutes per side until the coating darkens and the fish flakes easily.
While the fish cooks, combine the shredded cabbage, lime juice, and salt in a mixing bowl and toss until evenly coated.
Warm the corn tortillas in a dry skillet or microwave for a few seconds until soft and pliable.
Flake the cooked tilapia into bite-size pieces and divide among the tortillas.
Top each taco with a spoonful of cabbage slaw and several avocado slices.