The Traveller went to a system where she could confront the Darkness. That's our solar system. Humanity was chosen to fight alongside the Traveller. Was this the wisest choice? Was it the best choice? When humanity went to meet the Traveller, first contact with an unknowable entity that had been reshaping the worlds of our system, we did it armed with guns. Humanity bravely travelled across space, set foot on an alien and potentially hostile world, and walked up to a powerful, mysterious entity, and they did so only with rifles and courage to defend them. Humanity was the best choice for the conflict. Did this choice benefit or doom humanity? The Traveller did give us the Golden Age. We did end up suffering the Collapse, but there's no way of knowing if we wouldn't have been targeted by the Darkness or the followers of the Darkness sooner or later anyway. We know for sure that the Vex were active in this system billions of years before the Traveller arrived. I'm not sure if we know enough to say if humanity would have been better off without the Traveller.