I think we'd all expect a rather trite story line (well known) with some kitschy acting and a lot of fight scenes. It's not meant to be an artistic masterpiece.
I'm still wondering why Oppenheimer was thought to be some great movie, I think it went over my head.
Incidentally, the Hiroshima weapon was based on uranium and the design was never tested, they "knew" it would work, it was a rather simple design. They didn't spend much time on any of that. Maybe I said this.