If the launch is Zelda + Splatoon, yeah, I could see some people being a bit disappointed in that.
If it's those two + Mario and you're disappointed.....why are you interested in the Switch at launch. That's the dream scenario for Nintendo fans, based on what little evidence we had. If your dream scenario included Metroid and F-Zero, well, you were dreaming too much.
Definitely this. They're clearly trying to make the launch appeal to current Nintendo fans. that Wii U + 3DS base is the most important to get on board day one and the most likely to early adopt.
People who haven't been a fan of Nintendo from the Wii on, those who are sick of Mario and Zelda and didn't care for Splatoon, those sick of the iterative franchises like MK and Smash etc. aren't worth chasing at launch. Very few of those would early adopt even with a more varied library with Fzero, Metroid etc. as they're wary of Nintendo and most will take a wait and see approach anyway.
They're smartly catering to their base to generate early buzz and sales, and can bring those lapsed fans into the fold later as more games start rolling out and Switch is becoming easier to just walk into a store and impulse buy.
I'm somewhere between the "must buy day one!" fans and the wait and see lapsed fans as I enjoyed Wii U and 3DS, but as secondary platforms and have a lot to try to make time for on PS4 and PC this spring as is.
What I really want to see (and we definitely won't tonight) is how much of an improvement Zelda on Switch is vs. Zelda on Wii U. I still have my Wii U and if the graphics/performance difference isn't huge I may just play it there and wait and see on Switch for a bit. None of the other rumored 1st year games are immediate must plays for me--several I'll definitely play, but don't need to be part of the near launch zeitgeist.