The touch screen and the the Joycon accelorometers/advanced rumble aren't used at all in many games, or if they are, it isn't anything innovative. ARMS is an exception, though, but I really don't think many people bought the game.
The Mii avatar you create can't do much of anything. On the Wii U, Wii and DS there was a bit more you could do with those.
Amiibo aren't really useful except for small in-game bonuses
The companion app is currently lackluster. They could have made a Mario Kart 8 section where you compare your scores to your friends, a BotW section that would interface with your game... for now it's just a Splatoon app with a few nice features, with only one main feature actually communicating back to the game.
I guess those middle two aren't Switch-specific, but there are a lot of Nintendo-specific things that they should really considers spending time cultivating.
It's especially nice in handheld mode, where the user doesn't have a decent speaker system to emphasize things (and may not even have the sound turned on at all). In those situations, the user may not be able to hear the sound effect when they get hit by a shell or drive off the road. But with the rumble, the punch of it is still there.