Dude please.
Yes, it does matter. Considering that it's going to be combining Nintendo's home AND portable markets, and thus theoretically all the games you would typically have to buy two consoles for just to play. If they market it well enough, why WOULDN'T it matter for it to sell as much as it possibly can?
I've said in other threads that it likely won't sell on par with Wii, but that gen, as pointed out, was a special case. Having said that, and considering by all indications that Switch will at least be powerful enough to do respectable Xbone/PS4 ports, and that apparently everything in this fractured gen is getting to a "Scalable" point with all of of these "Pro" etc. releases, then IF Nintendo plays their cards right, markets it right, actually can get AND keep third parties on board, etc...there's no good reason at all why it couldn't still be more successful than 40-50 million units sold, lifetime. What they need are 1. THE GAMES, and 2. THE PEOPLE. People need to know about it, they need to be made aware of it, in an effective way, and they need to have games available for it that makes them want to own it. Period.
As for this "not unless Switch is the only new console you own" argument...honestly, not everyone is either willing or able to pour the kind of money it takes to have a decent PC gaming, rig, AND a PS4, AND an Xbox, AND a Nintendo system, AND a decent smartphone/tablet, etc. Not every adult gamer is a single or unmarried person, without kids to support, or major bills to pay, etc., and can just afford to pour money into a hardcore gaming habit. In fact, I'd wager most adults can't. Most adult gamers are probably lucky if they can afford a good gaming PC and ONE game console, or two game consoles. So it's 100% feasable that for some people, they might WANT Switch to be a viable "only new console I own" option. IF it can get solid third party support (big if), AND it has all those titles that Nintendo home console and portables usually get (IE both your major Mario/Zeldas AND your games like Pokemon), all on one system? Yes. That idea is very attractive.
And if you want that idea to actually take off, you want it to be as successful as possible. So it does matter. It always matters. Nintendo still has plenty of money, sure, but they took a major hit over how they mishandled Wii U, and they absolutely NEED Switch to be a huge success.