That's a two-sided coin. MK8 was a complete game whose DLC expanded the content to keep you coming back. Smash 4 is going to keep getting updates to balance the roster and adding Mewtwo seemed more like a late-in-the-game decision.
The Splatoon announced update seems more like what Lindy is saying in that the games isn't really done. It's a basic feature of other shooters that's missing and not just more levels (though that piece is there too).
As far as that practice goes, I agree with you. If Nintendo can sell me on a game and then give me more game later (free or not), then I'm for it. It keeps the game relevant. But this one is riding the fence.