Nintendo-published titles seem to be roughly 50% of Switch sales, so yeah, there must be a whole damn lot of people buying mostly or only Nintendo titles - I know I did!
That means the Switch will likely see fewer third-party games sold than the Xbox One despite selling way more hardware. Factor in the weaker hardware and cartridge costs to make the platform a little less attractive and you begin to understand the subpar third-party releases on the Switch.
If you consider Pokémon/Fire Emblem/Kirby not to be Nintendo games, that improves the share of the others a little, but these franchises are still typically Nintendo games in everyone's minds.