As a former student at Clifton College (Henry Newbolts school) this poem has special sentiment for me, for 'The Close' is where I spent the best years of my life. However I think anyone can agree this is a truly insightful and beautiful poem.

This poem to me is scarily insightful of the attitude that lead to huge losses of the First World War. Therefore I find it lacking in humanity and it is naive to the effects of war and detached from reality.

So how do you find it detached from humanity?
If anything, it illustrates it.
The fact that there is something more than the be-ribboned coat and the season's fame is something that can make humanity great. It shows why men were prepared to fight for what they saw as the greater good - for the acknowledgement that their deeds would live on.

Please tell me you were just trolling...

While Newbolt references the far-flung colonial battlefields that would have been familiar to his late Victorian readers, he describes an attitude, or approach, toward life that is equally applicable to sport, business, or, indeed, any of the myriad competitive arenas where individuals strive for success. The stakes may be serious (death itself), but he places value on this attitude, the "joyful mind" which equips his torch-bearers with both a greater chance of success and the type of style or dash which was viewed as the hallmark of the English gentleman of his day. The fact that this sort of enthusiasm can be perverted by politicians does not lessen its value.

"This poem to me is scarily insightful of the attitude that lead to huge losses of the First World War. Therefore I find it lacking in humanity and it is naive to the effects of war and detached from reality."

How much do you actually know about the First World War? Blackadder may be hilarious, but it is not realistic or a historical document and Secondary School education, with its focus on "how everyone thought war was lovely, then thought it was horrid and wrote poems about it" leaves a lot to be desired in terms of developing a real understanding of the War and developments in terms of changing strategy and tactics.
Perhaps you should procure the following book by Chichele Professor of the History of War Hew Strachan; the book is called "The First World War" and is a surprisingly short volume but still does much to dismiss the old clichés about silly old generals and poetic privates, and the myth of futility. That myth which tells fifteen year old children that the War changed nothing and just led to the deaths of millions in trenches and craters, this war brought down empires, fostered revolutions and laid the groundwork for the modern world, for good or ill, it changed everything.
And lastly it is not a poem naïve to the effects of war, it mentions the “sand of the desert sodden red”, what do you think it is sodden red with? It is “red with the wreck of the square that broke”, hmm reminds me of “Fuzzy Wuzzy”…

The images summoned here are of course not of the First World War, but of Rorke's Drift, or Khartoum, or the Khyber Pass, and such. The sentiment expressed is exactly that: a sentiment. C. S. Lewis said it best:

The glory of the old sentiment was that while it could steel men to the utmost endeavour, it still knew itself to be a sentiment. Wars could be heroic without pretending to be Holy Wars. The hero’s death was not confused with the martyr’s. And (delightfully) the same sentiment which could be so serious in a rear-guard action could also in peacetime take itself as lightly as all happy loves often do. It could laugh at itself. Our older patriotic songs cannot be sung without a twinkle in the eye; later ones sound more like hymns. Give me “The British Grenadiers” ("with a tow-row-row-row") any day rather than “Land of Hope and Glory”.
-- C. S. Lewis, The Four Loves

It is difficult to add much to the superb quote from CS Lewis but I think there is more to this approach to life than in being credited. To "play up, play up and play the game" means to understand that life is not too serious, follows rules, has fairness and justice as its base and is played for the team (or country) not the individual. Many accuse this poem of being an old fashioned evocation of empire but I think the values are fundementally Britain at its very best.