That's an interesting take. I would counter that the military hadn't changed a great deal from Napoleon to the start of WWI, and even in 1917 brass were struggling with how to counter the technological advances that gave the advantage to defensive positions. It would be another year before they figured it out.
Disagree with the feel since the respective trenches and no man's land were basically all the western front was about for most of WWI. Showing action from the front excepting the very beginning and last few months of the war there are utterly depressing and kind of unbelievable from a modern perspective. Take the last charge Schofield runs along-- in reality, dudes would still just be walking across the field with their heavy ass kits and getting cut down en masse by machine guns and artillery. I can see why Mendes would not want to focus on that. The Trench, Beneath Hill 60, Passchendaele and of course All Quiet have all trod that ground, and they're all more bleak with less commercial potential that 1917. Even the main conceit of the film -- the fuss being made over 1600 men -- is a little quaint given the hundreds of thousands of casualties experienced in battles like the Somme or Passchendaele.