Scale/Perspective:
OK takes up the bulk of the issues with the battle but its also the least likely to be an easy fix. So there are shots with a bunch star destroyers where they are scaled differently yet look like they are the same distance from the camera. This is because they all filmed separately and composited together, but they didn’t add any depth of field to the shots. For instance the size of the SSD next to an ordinary SD:
There wouldn’t be any visible depth of field at that scale. It’s like photographing mountains from a distance, they would all be in focus.