I suspect many of the positive reviews are not impartial or by reviewers who missed Full metal jacket, Dunkirk, Platoon, All quiet on the Western Front (1930) etc etc.

One of the biggest problems with this film is the two young protagonists. Both boys are very forgettable and lack any kind of gravitas to carry a film on the big screen. As a result it's very hard to care about them and their video game like quest. Though this problem is not entirely their fault.

The script is run of the mill (didn't people curse in those days?).The director doesn't employ necessary dramatic close ups to break the mundane midshot. We don't effectively see their blood, sweat, tears and the horror or determination in their eyes. Also the panoramic shots aren't particularly panoramic. The scale of the battle fields and surrounding areas are poorly filmed. The cinematography as a whole wasn't up to the scale of story.

At the end of the film one gets the sense you've just sat through a long YouTube video of mice in a maze with a few fx thrown for fun. However, this film could be a very good two part BBC miniseries.