That seems to be a common complaint with Nolan's films. I recall similar statements about Interstellar and the Dark Knight films. I'm not sure why he does that, as it must be purposeful.
I don't think the trailers are doing a very good job. I generally like war films and period pieces, but I've seen quite a few trailers and don't find them particularly enticing. Still undecided whether to see this or not until I hear some reviews.