Preheat the oven to 425°F (220°C). Line a large sheet pan with parchment paper or lightly grease it.
In a large bowl, combine the olive oil, chili powder, smoked paprika, ground cumin, garlic powder, onion powder, crushed red pepper flakes, kosher salt, and black pepper. Stir well to create the fajita seasoning mixture.
Add the shrimp, sliced red bell pepper, yellow bell pepper, green bell pepper, red onion, and pineapple chunks to the bowl. Toss everything together until evenly coated with the seasoning mixture.
Spread the shrimp and vegetable mixture in a single layer on the prepared sheet pan.
Bake in the preheated oven for 12 to 15 minutes, or until the shrimp are opaque and cooked through and the vegetables are tender-crisp.
While the fajita mixture is baking, warm the flour tortillas in a dry skillet over medium heat for about 30 seconds per side or wrap them in foil and warm in the oven for 5 minutes.
Remove the sheet pan from the oven. Use a spatula to transfer the shrimp and vegetable mixture to a serving platter.
Garnish with fresh cilantro leaves and serve with warm tortillas and lime wedges on the side for squeezing over the fajitas.
Assemble the fajitas by filling each tortilla with the shrimp and vegetable mixture and adding extra lime juice if desired.