Honestly, I didn't care if it is a one shot movie or not. The cinematography is purposeful, feels like following the journey while just glancing over the characters the hero(es) interact with. The one-shot illusion helps in achieving that. There's no need to mention the beauty of the movie, as Roger Deakins shot it. I resisted.
One thing I noticed in the movie is the use of mid-horizon. In The Fabelmans, John Ford says to the Steven based character not to use mid-horizon, but imo in 1917 it gives a more grounded (read mundane) feel to the movie. It's as if there's nothing extravagant happening in the war, which is true, and at this point, it has just turned into a routine of violence for soldiers.
This brings me to Benedict Cumberbatch's Mackenzie. He beautifully summed it up in one dialogue "There's only one way this war ends, Last Man Standing." It's as if telling that the war has become so mundane that it'll go on until one side is obliterated.
The background music is good, though I find myself comparing it with Dunkirk's score, which is another masterpiece.
Verdict: Masterpiece. Simple story, brilliant execution.
You'll be missing out on a beautiful simple story if you don't watch it. That being said, I was in the right mood for watching this. In morning, I was playing COD WW2, in the evening I watched 1917. Playing the game got me personal with the war. So, that helped.
Finally, go watch it if you want a feel of how war is a thing that never benefitted those on the battlefield.
Rating: 10/10 or 5/5