You may often see or hear this statement from well-meaning veterinarians. In their experience, they have only seen poor results from traditional high starch/carb dry cat foods often fed to our carnivore cats.
What your vet may really be concerned with is the hydration of your cat. Conventional thinking is that any canned food will produce better hydration than any dry food. But, if you compare a canned food with 15% starch and a dry food with 15% starch, you will see the same hydration level in the cat when fed either diet. Research shows that as the starch level of any diet increases, a cat consumes less water on a daily basis. It has nothing to do with whether a diet is dry or wet, but the diet's starch content. Properly balanced animal protein and fat is also critical. Your cat needs two-parts animal protein to one-part animal fat. In other words, 48-50% of their calories should come from protein and 50-52% of their calories should come from fat.
All of Young Again's cat foods contain less than 6% starch/carbs and our ZERO formulas contain less than 1% starch/carbs. Your cat is an obligate carnivore and when fed a properly balanced diet, dry or wet, she will stay properly hydrated. For more information, read our article on Feline Hydration: Wet vs. Dry.