So sorry to hear about your kitty. I'm probably not the right person to answer because I don't have any pets. But I'll give you my uninformed take on things.

There's life and there's life worth living. Only you can make the call. It's hard to separate what's best for our fuzzy friend and what's best for us. Who knows, but 23 is a good life lived up to now.

I had a cat, Fudge, that I got when I was in the 5th grade. I was 10. She died when I was 30. That's not as old as your cat, but that was most of my life at that point. My brother and father were going to take her to the vet that morning to put her down because she had stopped eating and was no longer functioning properly. When my little brother went to put her in the box, she was gone. Unfortunately, things don't always work out so neatly.

Hugs to you and Big Kitty!