Bring a large pot of salted water to a boil. Cook the elbow macaroni until al dente according to the package directions. Drain well and set aside.
Cook the carrots and cauliflower until completely tender by steaming or boiling. Drain thoroughly.
Transfer the cooked vegetables to a blender or food processor. Add a little milk and blend until completely smooth.
Melt the butter in a large saucepan over medium heat. Stir in the flour and cook briefly. Gradually whisk in the milk until smooth and slightly thickened.
Stir the blended vegetable puree into the sauce. Add the garlic powder, onion powder, paprika, salt, and black pepper.
Reduce the heat to low. Add the cheddar cheese, mozzarella cheese, and cream cheese. Stir until completely melted and smooth.
Add the cooked macaroni to the cheese sauce. Stir gently until every piece is evenly coated. Add a splash of milk if the sauce is too thick.
Serve warm with an optional sprinkle of shredded cheese, paprika, or black pepper.