Yeah, I don't see why people think this is an issue. If this sells how Nintendo hopes, than a large amount of Switch owners will have never played these games anyway, and it allows them to come screaming out the gate with a software lineup that will actually help people get serious use out of the device.
Whether they are enhanced ports with additional content or not, launching a new Nintendo device alongside Zelda, Mario Kart, Smash, Splatoon, and Mario Maker is good for everybody. Mario Kart 8 isn't suddenly no longer a fantastic game just because Switch is out, so why make us wait until halfway through Switch's lifespan to make a new one from scratch when they can just port the previous one and add more to it? Same with Smash.
Customers weren't interested in the Wii U itself, not the games it had. I have lots of family members who love Mario Kart 8 and Mario Maker, but the Wii U itself is unappealing to them. They hate how the Gamepad feels, they think it's too expensive and I've actually heard a lot that people don't like that the Gamepad can't be taken on the go to play the games, so they don't want it. Lots of my friends come over and only want to play Wii U when they're here, but refuse to buy one themselves.
These games are appealing to people, they were just stuck on a piece of hardware no one wants.
EDIT: Not the best analogy, but still, think of Resident Evil 4. That game was initially stuck on the worst selling platform of that generation. That didn't mean people didn't want RE4, they didn't want the Gamecube. When it came to platforms more people liked, the game continued selling like gangbusters.
