I think you could pretty easily undermine the jingoism. In fact, I think the story (especially Walter's death) does that itself, but portraying the jingoism is an important thing, because it was very real at the time.

More likely there just isn't a budget for it. We have a film/tv industry, but the period dramas tend to be stalwarts that have been running for nine hundred years and frankly barely count as period. (Murdoch Mysteries.)

That makes sense!