So I agree with your last thought that Kafka devalues the human, in order to make it show itself. Incidentally Metamorphosis cannot be a response to what he experienced in the 1920s as he wrote it early on, in 1912. Also A Country Doctor does not end in death, only in failure. The human perhaps shows itself in failure. All the stories cited are in their own way tragedies.
Tragedy touches on human nature by showing human failure.
Through that the nobility of the individual can show itself.