Your view is that it is impossible to get the same nutrients without killing another animal? Do you mind naming which nutrients you feel this way about?
For cats especially, yes. And no, I'm not going to do that. It's on you to prove that they can, and so far all evidence (other than this guy who is shilling his own food, surprise, and using unreliable self-selecting and self-reporting data) says otherwise.
It's not on me to do anything. I have no cat. I also have no idea if a cat can be healthy without eating meat. In fact, I don't even know if it is cruel to keep a natural born hunter in an environment where they almost never get to hunt live prey. When people have snakes they feed them live animals, and I'm not sure why cats get deprived of that instinct by their owners.
Personally, I prefer relationships where everyone involved is free to do as they please, so forcing a cat to live in a house so I can always have company just feels a bit like something I wouldn't enjoy. I think it is more on me to deal with whatever problem I have with being alone instead of forcing someone else to be my captive.