From the human perspective, the death of our species would represent the ultimate failure. But the wisdom of Nature provides a radically different appraisal. We are a successful species if we are serving as a forerunner of the next complex species. But for this species to be realized, we must relinquish our dominant position on the planet. Otherwise, if that species tried to find a foothold, we would summarily exterminate it.
Humanity is the kudzu of the animal kingdom.
To see ourselves as successful, we must adopt the perspective of Nature, which is indifferent to human puffery. We must think of ourselves as parents who are ready to step aside to make room for their progeny. Relatively few humans are humble enough to adopt the broad perspective necessary to accomplish this. The vast majority find it unacceptable to surrender their existence for a species they can't understand or appreciate. Indeed, many parents even find it unacceptable to step aside for their own children.