Function to me means function in all parts of life. Career, social, private.

Many people seem to not to function in some of these. Kafka's love life was a mess. He had problems with his family. Struggled with his spirituality. He never really wanted to his books published... his friend did so against his wishes.
So I see him as example of somebody who struggled majorly. But at the same time, wouldn't be helped by being pushed to be just like somebody else, not to make people uncomfortable... and so on.