It's a fail. They shrunk their addressable market. They replaced a successful home and mobile business with a mobile only business, and are selling worse than the 3DS but have no home console sales at all. You can't spin Nintendo leaving the market as a success. If Microsoft stopped making an Xbox, that isn't a success.
What on Earth?
1) They are successful half the time and unsuccessful the other half in the last decade. Wii Ds was success. Wii U 3ds was failure that lead to operating losses or breaking even.
2) Switch is tracking way ahead of 3DS. It's actually ahead of Wii and close behind DS right now. And unlike 3DS, they didn't have to slash the cost a whopping $80 to sell it months after launch. They are making far more profit on each Switch sold than 3DS, and they are selling far more Switches than 3DS did.
3) It is a success if they make more profit each year and it appears they are.