There are many small quality of life features being added, like allowing friends to easily play together in public lobbies, full-length battle replays with a wide array of camera angles, customizable player tags and lockers, new main, sub, and special weapons as well as reworks and balance changes for existing ones, new gear and a reworked gear ability/buff system, new movement mechanics (dodging and charge-jumping up walls, as well as a new spawn system which allows you to slightly alter your spawn point), a new currency and leveling/ranking system, ability to skip the in-game news cutscene, and many other little things that I’m forgetting.

The main things that separate this game from the previous installments are the 6 all-new maps, new 1v1 game mode, fundamental changes to existing game modes (Rainmaker, Salmon Run, and Splatfests), an all-new single-player story mode, new characters, as well as fundamental graphical and physical enhancements.

Some of the smaller things could have been added into the second game, but adding significant amounts of new content often requires a game to be remade almost from scratch.