Honestly, I think Splat 3’s reception would be better if it had simply been more inventive with its aesthetic.
Like, Salmon Run had no reason to look the exact same as the version in 2 yet it looks almost identical. The hub is just a more busy, less ‘modern’ version of what we’ve had twice before. The shopkeepers share almost identical character archetypes. The enemies in SP are just the same as 1 and 2’s but with some hair, and the levels are still just random floating platforms in a void. The idols have the same ‘one is more mature with a darker colour scheme, and one is childlike with a lighter colour scheme” dynamic going on. Outside of a single map, the multiplayer levels just look like the ‘inner-city’ stuff we’ve had before (and that’s if they’re not direct aesthetic copies from the predecessors). The UI looks the same, the clothes share similar styles, and so on.
Say what you want about CoD, but the aesthetic changes significantly from year to year to always keep things fresh. It’s always gonna be ‘realistic military’ stuff, but it does a lot with that framework. Splatoon 3 doesn’t, with its whole ‘chaos’ theme amounting to a single map, a main character with a slightly-tattered t-shirt, and a small chunk of the single player.
If it had overhauled the UI, changed the looks of every weapon, changed the art-style of new and returning maps, and focused on differentiating it’s character designs, the game would have felt inherently different even if the fundamentals were all familiar.