Dunkirk is a beautiful and unconventional World War 2 epic that is undoubtedly captivating, but it takes risks that may alienate some viewers. 
When people talk about a film they think it's about the setting, but it's actually about the characters. Saving Private Ryan isn't about World War 2. It tells a story about a squad of soldiers tasked with finding a young Private Ryan and getting him back safely to his family. Saying Dunkirk is a film about the Battle of Dunkirk however, is not inaccurate. The setting and characters are one. The choppy waters of the English Channel are equally as important, if not more so than the people who fought and died in them. As much as this makes for an interesting way to make a mainstream war film, it's also the reason why I wouldn't care to sit through it again. In some ways, it feels like watching a documentary with the narration turned off. 
I walked away impressed, and at the same time emotionally and intellectually unfulfilled.