I've always fed my cats the cheapest canned tuna in water people food with a side of dry food and a bowel of water.
Everyone told me i was nuts.
My current one is 17+ years old. The previous two lived 19 1/2 years and 18 years.
Actually we do the same. I have a Tortie Point Himalayan " Miss Betty " that only like albacore warm out of the can.
My hubby adores her and gives her her way 2 times a week. She just eats a little bit with juice. He takes the left over and feeds wild critters in back of the office complex he works. HAAAAA. He even likes raccoons and other creatures.
You aren't nuts, if you are, we are too. Staying away from that cuts and gravy is a good idea. Lost my Norwegian Forest cat 2 years ago. I was nuts for him. He talked.
By the way, all of ours are over 13. We have 4 left. Our family that still resides with us!