Incredible reviews aside, the reality is that Dunkirk is an excellent film, but not an excellent film compared to other Christopher Nolan films.
Nolan made an interesting choice in approaching this story. He took the enormous historical event of the Battle of Dunkirk, and decided to tell it via three relatively small plot lines. Each is well crafted, and the glue that holds the harrowing scenes together is Hans Zimmer's wonderfully chilling score. The acting is solid. There are great moments of visceral impact. At times the cinematography is excellent. At times it's a little blasé. Though at its best, as in scenes of ships sinking, and soldiers fighting for their lives via canted angles, the film delivers brilliance.
Dunkirk is a showcase of a monstrous event. There are few character arcs, few deep relational interactions, few moments when a character's growth wows us. Instead, the wow factor is in the showcase. Therein lies the problem. Dunkirk is a $100M film. It plays much smaller than a recent $40M war film, Hacksaw Ridge, which had the deep emotional arcs satisfyingly imbedded into it, along with wow moments far more impactful than those found in Dunkirk.
I recommend seeing Dunkirk. It's much better than the vast majority of war movies out there. Yet, coming from whom many consider to be the best director of our day, Mr. Nolan was outdone by Mr. Gibson, and not by a narrow margin.