If I do feed kibble, it's never plain... my dogs will scarf down plain kibble, but I like to soak it in water or broth, and I believe in feeding as much fresh food as possible.
I add chicken, egg, cottage cheese, canned salmon, canned 100% meat dog food, salmon oil, goat's milk/cheese, veggie puree (usually tomatoes, carrots, greens, and broccoli), kelp, plain yogurt, etc. Healthy leftovers, too. It also saves on how much kibble you're feeding.