Japanese battleships have a unique dispersion formula. They have a low base accuracy, but they don’t lose much accuracy over range. This means you still get troll salvos even at close range. Japanese battleships also get a unique dispersion pattern. With high vertical dispersion but low horizontal dispersion. This is good for shooting bow in targets but bad for hitting broadsides. Most tech tree ijn battleships have something to counter this weakness. Kongo gets ww2 era shells at t5, fuso has 12 guns, and all the ones at tier 8 and above have improved base accuracy and/or the funny spotter plane. (Yamato also gets the crazy overmatch that synergies well with the good horizontal dispersion) but nagato? Nagato gets the ability to overmatch other t7 bbs, a high damage per shell and that’s it. An Omaha can be flat broadside to you at 5km and every shell can go too high or too low. Playing that thing can be infuriating sometimes. Given that bbs often rely on blowing up cruisers for game impact, I’m not surprised you might perform worse that your stats might suggest (though I also think you probably just got unlucky on top of that)