I would argue that the Splatoon 2 and 3 DLC is the best content in those games, far outstripping what the main SP campaigns were doing (and certainly better than the MP, but I've never been a big Splatoon MP guy).
Playing through Raiders, I'm not loving that pretty much the ENTIRE focus of the game is on the not particularly special Splatoon series combat instead of the platforming, but the game's been decent enough so far.