Yeats was 18th-century oratory, almost.
Every time you read a poem aloud to yourself in the presence of others, you are reading it into yourself and them. Voice helps to carry words farther and deeper than the eye.
The gift of writing is to be self-forgetful, to get a surge of inner life or inner supply or unexpected sense of empowerment, to be afloat, to be out of yourself.
But death is not easily escaped from by anyone: all of us with souls, earth-dwellers and children of men, must make our way to a destination already ordained where the body, after the banqueting, sleeps on its deathbed.
I can't think of a case where poems changed the world, but what they do is they change people's understanding of what's going on in the world.
It is always better to avenge dear ones than to indulge in mourning. For every one of us, living in this world means waiting for our end. Let whoever can win glory before death. When a warrior is gone, that will be his best and only bulwark.