The Wii + DS combo was a complete monster. The PS3 + 360 + PSP numbers combined were close to matching the Wii + DS combo but still fell short.
For the Switch, 17 million in a year (or fiscal year) is nothing to scoff at. The install base will continue growing as games continue being developed and released. No, the Switch is not the Wii, but it doesn't have to in order to be considered successful.
Honestly I think it could reach Wii levels, it wont have as high of peaks but if handled correctly it could have longer legs.
When the herd loses its way, the shepard must kill the bull that leads them astray.