Put more simply, he's saying art is the product of, and the expression of, human emotion and experience.

Suffering just happens to be a common element of that, but it's not essential. Maybe because it most commonly produces good or great art. People generally don't make art about how their love life is perfectly fine, instead they express their experience of devastating heartbreak.

Nike Cave is just one strand of the artistic experience. Contrast say Kraftwerk, whose expression is about feelings of affinity with machines, technology and even interaction with transport infrastructure.