The first thing I noticed was that it takes place in the future. So really, it's more of a sci-fi film. It should be said that the word priest is not reserved only for Catholics (Episcopalians/Anglicans use it, as well as many early religions). From what I've seen, I don't think that the filmmakers were thinking, "This is the way the real life Church is let's portray that." The way many storytellers and filmmakers get their ideas is by asking, "Suppose..." I think what they were trying to say is, "Suppose in the very distant future (look at the technology) the Church is hijacked and became this unrecognizable other religion..."
I don't know, as a writer myself, that would seem like an interesting story I'd like to write.
This seems like one of those movies that to get a true sense of it you need to watch it. Remember, a trailer is 2 and a half minutes long out of a 2 hour movie. I don't expect them to tell me much in the trailer. I didn't even know by watching it that he needs to save his niece. All I know: future, weird futuristic church, a priest, vampires, lots of action. That doesn't tell me much. I think if we draw conclusions based on the trailers, we could be missing a lot. We are going to be missing a lot.
So I think that if you're into sci-fi or maybe you want to see what the film has to offer (you never know, maybe it has some symbolism or meaning) go see it.