History is a problematic subject because it creates false dichotomys all over the place. When actually sacrifice for your country, your community, or your friends is admirable. It is also an utterly pointless waste. A waste that can be justified at some levels of abstraction but not at others. These points are not inconsistent. But people want to take one simple truth away from the complexity. History has obvious lessons in hindsight and can be turned into trite propaganda in the moment.
Agreed, history is very problematic, it can and does create false dichotomies.
My comment and your reply provide an excellent example of why it's so difficult to post an adequate reply in short HN posts (see my detailed reply to anm89 in response to a similar issue).
No doubt, self sacrifice can end up being noble in circumstances where such action contributes to an overall better outcome but that's not the general case with WWI. (Please, I know that statement is grossly inadequate and that in specific 'local' instances it's not even correct—given that many of those soldiers who made such hugely noble sacrifices did so in order to directly benefited their buddies—not the nation state that actually sent them to war – however that explanation will have to suffice for now.)
Whether Owen fully realized it or not, the reason why his poem is so often associated with the negative aspects of Dulce et decorum est pro patria mori is that in the real political context of the First World War it is an undisputed lie.
At the time, if the average soldier, French, German, English, US etc., etc. had been fully informed of the actual reasons for the start of said war—the horribly degenerate state of the underlying politics of the nation sates involved, the pathetically inept and inbred thinking of both English and European monarchies—just to mention a few, then these soldiers would likely have walked away from those hellish battlefields and left the fighting to the protagonists who actually stated the war.
In short, millions of lives were lost unnecessarily over inept and faulty reasoning and the many 'petty' squabbles that occurred at both domestic political levels and similarly with international politics wherein diplomacy failed most spectacularly with enormously disastrous and tragic consequences for just about everybody. Moreover, many of these issues were never fully resolved let alone properly handled at war's end—Versailles and all that—which, in the end, led to WWII and even many more millions of unnecessary deaths.
If ever there were a war to make Dulce et decorum est pro patria mori the ultimate lie then the First World War has to be its quintessential example (it's why I selected it as the example).