All our cats, including the 20-year-old we have now have lived long happy and healthy lives. We feed them both canned and dried as well as some "people food" whenever they want it. Also an occassional can of tuna. I think they need at least some dried food because it contains some fiber and roughage which is good for their digestive system. Let me quickly say that I assume
it's good for them, based on experience. I'm not a veterinarian, but I've kept cats all my adult life and I'm pretty old.
We also are very careful to keep them supplied with fresh water -- probably good for their kidneys and urinary tract, etc.
Our cats are also allowed to go out of doors, which most cat owners say is dangerous and a big no-no. But I want them to have their freedom. They also eat grass outside, which is (I think) good for them too. During the short winters here, I grow grass inside for them.
Jeez! What pampered and spoiled kitty cats! Eh?