I think you have a point when you say that the film didn't emphasise the scale of the evacuation. If you didn't know any better, you'd be shocked when Kenneth Branagh's character mentions towards the end that they got 300,000 men of the beach. However, I still enjoyed the way it was told all the same. I think too big a focus on the scale would risk endless comparisons with Saving Private Ryan.
I thought it was generally excellent. The way the tension was wound up when the German bombers were lining up the boats / beach was extremely engaging. The one main criticism I would have is the lack of blood and guts which took away from the realism. And as mentioned above, it got a bit jingoistic at the end.