Death is the separation of body and spirit.
A person can leave their body in their spirit and not be dead.
However, their body would be nonresponsive.
Without a body there are no inputs to feed information to the brain and spirit.
The spirit does not die. That is what the scriptures say.
Matthew 10:28 Do not be afraid of those who kill the body but cannot kill the soul. Rather, be afraid of the One who can destroy both soul and body in hell.
That scripture is saying that men cannot kill the body with the spirit (which together is a soul), but they can kill the body.
There is no optical or audible information to process. There is no sense of touch or smell or taste.
A spirit can see, move, talk, think, and feel emotions.
God created the brain to process information but the brain of a dead person is nonfunctional, no information can be input or processed until God provides a new brain at the resurrection. The person's spirit will join with the new brain and the person will live again with no awareness of the time out.
You are speaking as one who will not accept what the scriptures say about the spirit. The scriptures even speak of ghosts/spirits.
Jesus does not rebuke his disciples for thinking he was a spirit. Jesus tells them that a ghost does not have flesh and bones.
So then, you see it is not as you say. A spirit does not need a body to exist.
Luke 24:36 While they were still talking about this, Jesus himself stood among them and said to them, “Peace be with you.”
37 They were startled and frightened, thinking they saw a ghost. 38 He said to them, “Why are you troubled, and why do doubts rise in your minds? 39 Look at my hands and my feet. It is I myself! Touch me and see; a ghost does not have flesh and bones, as you see I have.”