As someone who did watch the movie, Oppenheimer does mention the effect of the bombs, and it's even shown as a pretty big deal to the guy. Like yeah, it shows him helping pick out the targets for the nukes, which we all know he did in real life as well, and shortly afterwards he is shown a slideshow of the effects of the bombs and the damage it did to the cities that got hit. Obviously the movie is going to mostly focus on the psychological effects they had on the guy who made them, since the entire movie is about him. Hell, I felt that it indirectly statted by the movie that Oppenheimer become a vocal critic of both President Truman and the atomic program of the US precisely because he did see those pictures of the devastation brought on by his work on the bomb.