The problem is that cats can't evaluate risk the way humans can. A cat may choose to go outside, just as it may choose to run across a road, approach a coyote, eat something toxic, or wander onto someone else's property. We don't usually treat an animal's immediate preference as the final authority on what's best for it.
A cat wanting to go outside isn't evidence that unrestricted outdoor access is in its best interest any more than a dog wanting to chase traffic is evidence that traffic is safe.

"Right to die" is a medically assisted death that is available in certain places around the world. If you can't make peace any other way, moving to a place where this is an option may be the most helpful thing for you.