The songs written about WW1 long after the event are really about the time when they were written - Bogle's "Willie McBride" [No Man's Land] and "And the Band Played Waltzing Matilda" are songs about the Vietnam War.

Usually people do that when they don't have the imagination or courage to take on issues from their own time in their own terms. The godawful legacy of Jacobite cliche songs about 1745 is another example of the same process.

WW1 songs that actually date from WW1 are a lot more interesting.