Lots of factors here.

Suggested reads: Face of Battle by Keagan (noted above), Tuchman's Guns of August.


Yes, the influence of close order drill on military thinking was a persistent issue. Close order drill had been the dominant element in troop discipline from the 1600's onward (and probably was central to Republican/Early Imperial Rome as well). Pscyhologically, soldiers enjoy the close company of fellow soldiers when facing battle -- but high explosive loves the bunched up targets.

Countries at the time were nations-in-arms, but had upper leadership groups that truly believed in the decisive battle. The greater ability of industrialized nations to persist in conflict despite major reverses in the field had not truly penatrated the thinking of most. There were exceptions like Kitchener, who insisted on preparing and army of millions while his countrymen thought the conflict would be over before Christmas. Both sides believed that it would be like the war of 1870 -- one great campaign and series of battles lasting no more than a season or so would decide the outcome. Look at the military plans of the participants at the outset; only the Germans had a technique that might have achieved decisive victory, and even their efforts fell short as a result of limited tactical mobility and the inevitable friction of war.

The ability of the defense to inflict casualties and the relative lack of improvements in mobility as compared to firepower doomed the participants to a war of attrition on any front where terrain or total troop density per square mile reached beyond a certain level. There were glimpses of the future -- the taxis of Paris shuttling troops to the Marne, the hit-and-run efforts of British Armored Cars in Belgium and Northeast France, but in general you had great strategic/logistical movement with limited tactical mobility. Where mobility was still possible because of more open terrain and lesser troop densities -- Palestine/Mesopotamia/Arabia -- the war was much less of an exercise in futility.

I don't know that I'd emphasize the "Colonial" element in the way you do, either. It is not as though the South Africans, Americans et. al. were more innovative than were the European locals. The Western Front was just the side with the "deepest pockets" eventually forcing the opposition to quit the game. The most successful efforts -- the stosstruppen tactics -- were pioneered by younger (and presumably less hidebound) German infantry leaders, but its not as though Ludendorf and others weren't willing to adopt them. Also, the great technology changes of WWI have already been noted.