Aside from all of the other reasons we think this will be a piece of shit, let's not forget the whole "they didn't have orchestras back then" bullshit. What are the chances that a Christopher Nolan movie has an amazing fucking soundtrack without an orchestra? I mean, it might be decent and we might not really notice its lack unless we are looking for it, but one thing about Nolan's movies is that they were almost universally recognized for having standout soundtracks that you can't help but notice. Fuck, Inception literally rewrote movie trailer sounds with the "BWOOOOONG" sound.
Can a movie have good music without an orchestra? Absolutely. Can an epic mythological tale with a massive budget, special effects, action set pieces, etc. have "holy shit" level music without an orchestra? I'm skeptical to say the least.