I agree with genetics engineering as the answer.
Our DNA has greed, power tripping, paranoia etc. hard coded somewhere. The correct combinations might stop all wars.
But all in all, wouldn't it make humanity dull and unsatisfied? I wonder.
I'd argue that humanity is humanity and we wouldn't remove its complex emotions, philosophical wonders and existential dread.
Desire for more out of life, search of meaning, etc.
Unless we go all the way and engineer ever flowing euphoria from birth to death, for everyone. But then, what's even the point?
Eugenics is often conflated with "selective breeding", which is pretty justified, given all the derives from the twentieth century.
Today, whether we should include CRISPR and so under the umbrella of eugenics is still open for debate.
The term of Transhumanism may be more relevant in this specific topic, as for Wikipedia's definition,
Transhumanism is a philosophical and intellectual movement which advocates the enhancement of the human condition by developing and making widely available sophisticated technologies that can greatly enhance longevity and cognition.
On a personal note I think that all in all, defining what are the " good genes to add, remove, or keep" in the human pool is definitely a delicate matter, 100% biased by our cultural differences and steps fully in the endless philosophical field.