Yep, thought exactly the same! (my daughter keeps insisting it's a totally new game, but to me it still feels almost identical to the WiiU version, except with a few minor (albeit welcomed) improvements.
One thing I will say that I am glad about with the Switch version though is that all controllers you play it with allows you to position your gun aim via motion control (even the JoyCons on the JoyCon Grip)., whereass on the WiiU version, on;y the GamePad player allowed you to do that, but the additional players could only position where they were looking with the thumbsticks, so put them at a complete disadvantage (as it's much slower to do that with the thumbstick, so by the time you've oriented where you are looking, you just get shot several times by everyone who can aim more instantly). So the Switch version was definitely an improvement in that sense, as now at least all players are equal.
One thing that did surprise me though, is that while I initially thought I would prefer playing in GamePad mode because of this, what I actually found in practice during my global test-fire session yesterday was that it was actually easier to play in KickStand mode with the JoyCons in the JoyCon Grip than with them attached to the tablet. (Mainly because the joycon grip being smaller meant there was that little bit less distance to travel, so I found I could accurately position much quicker, because the pivot angles were not so steep in order to get from position to position, whereas it took much more effort to pivot the GamePad so quickly in GamePad mode. So for the first time ever, I found myself greatly preferring the JoyCon Grips for this game. (I still prefer GamePad mode for Breath of the Wild though). So it's worth experimenting sometimes, as what woks best in one game isn't necessarily the same in another.
However, because of playing this way for Splatoon 2, it was also was the first time I actually had my JoyCons run out of battery during play. So I'm kinda glad now that I had bought the more expensive charging grip (as just playing breath of the wild, I never needed it at all due to the JoyCons continually being automatically charged by the tablet, so they just never ran out). So for a long time I was beginning to think I had wasted my money buying that thing, but now it's kinda making alot more sense why it's sometimes necessary to have a charging grip handy)