Your macaroni salad may not be creamy if you used too little mayonnaise or dressing, or if you overcooked the pasta and it absorbed too much liquid. To make macaroni salad creamy, you can mix in more dressing, such as a combination of mayonnaise, mustard, vinegar, and seasonings, until the pasta is well coated and slightly saucy. You can also add other creamy ingredients, like sour cream, yogurt, or whipped cream, or moist ingredients, like diced pickles, relish, onions, celery, or hard-boiled eggs, to enhance the texture and flavor of the salad. Mix the macaroni salad well, and let it chill for at least an hour before serving to let the flavors meld and the dressing thicken.