I think it's easier to consider which target groups the Switch will have a hard time with and go from there:
Handheld market:
-Switch has weak battery, $70 games if Zelda is any indication (in comparison 1st party 3Ds games are about... $40), paid online play which is something entirely new on the handeld market (possibly extending to basic features as simple as trading in Pokemon games) and very big size (comparison shots show it to be as big as the WiiU gamepad unless you carry the Joycons around seperately, and even then it's quite a bit bigger than the Vita) and is heavier than the WiiU Gamepad according to people that tried it out at events.
- The price is $300+. Experience shows that the 3Ds barely sold at $250 and everyone knew that Pokemon mainline games were coming to that device. It took drastic price cuts and the ambassador program (and the current Nintendo president Kimishima stated that he is completely against handing out games for free) before it took off
- The Vita already tried "huge screen for a handheld and console games on the go!" as a selling point. We know how that went
- Some games might run quite badly in portable mode if developers focus on docked performance
+ Switch will have Pokemon. On the other hand people that want to play them will have to pay for online, pay 43% more for the game and there won't be a $70/80 2Ds for people coming from Pokemon Go to pick up the newest game
Console market:
- Switch releases mid point of the current generation. The console market is dominated by the PS4 and the XBone to a lesser extend. Both of them have huge gaming libraries and 2017 has an insane line up for games
- During the Christmas sale the PS4 (500GB) went as cheap as €200 in Germany. Right now you can pick up the same console with Uncharted 4 bundled in for $268 on Amazon.com, with Microsoft constantly trying to undercut those prices with the XBone.
- PS4 Pro is only $100 more expensive than the Switch... and only €70 more in Europe
On the other hand the Switch will release at $300 and even €330 in Europe...
- While having far less power to woo tech enthusiasts (and the Scorpio coming out this year which is The Mountain compared to Tyrion Lennister when it comes to technical prowess)
- All those consoles mentioned above are likely, particularly in the case of the Pro, to have even further price cuts that will keep them ahead if Nintendo decides on a WiiU pricing strategy
- PS4 and XBone have massive 3rd party support, including massive franchises such as Call of Duty, Assassin's Creed, Halo, Souls games etc. etc., something that the Switch will barely have (particularly because of underpowered hardware and past experience), so it relies (again) on the appeal of Nintendo's first party software
- While having a really sad launch lineup which basically consists of BotW and nothing else of note
- Hilariously overpriced peripherals compared to competition
- If developers decide to prioritize the "handheld mode" then game performance might suffer in stationary console mode
+ Pokemon, Monster Hunter and Yokai-Watch likely to move over to switch. Sucess remains to be seen (particularly in bringing over the current 2Ds/3Ds base, see 'handheld market'), home console Pokemon games have been quite a bit behind the handeld mainline games in sales so far (Stadium, XD, etc.)
Casual Gamers and parents:
- Dominance of mobile games and devices such as tablets and smartphones (and particularly smartphones are used by almost everyone and almost everyone needs one anyway), for which games can be gotten at the price point of $1 or "free"
- Giving your children your old phone/tablet keeps them occupied without further investment
- Switch is expensive at $300... without games
- $70 for games
- Online play Subscription (which your kids will want if they play Pokemon and want to trade/fight with their friends) , technically complicated and likely easy to damage, replacement of components and peripherals is very expensive if something is lost/damaged
- For home console use eg. for children, see 'console market', particularly price compared to competition is standing out for this criteria
So, basically that leaves the following groups where the Switch has a big appeal:
- Nintendo faithful and those that absolutely need to play new Nintendo 1st party software (at least if they are not buying it on the WiiU instead, at least in the case of BotW)
- Harcore enthusiasts that need to own every or most consoles
- Potentially the Vita base (though possibly with much less Japanese 3rd party support) for the handheld aspects (high price, big, console games on the go)
- Wii U owners that want to upgrade and can look past above points
- Motion control enthusiasts that couldn't get their fix with the DS3/DS4 gyro controls/tilt (barely any games use(d) those features) or Kinect (we know how that went with the XBone) and casual motion control game enthusiasts that can look past the points in 'casual gamers and parents' (in reference to "Switch will recapture the Wii audience!" arguments)
So mostly the groups that the Wii U appealed to and covered to large parts. Not much considering the small install base the Wii U had. And I left out potentially rather harmful points such as the Online Subscription (e.g. imagine a 50/60 $ price tag for what they announced it will offer), how pricy the online gaming subscription might turn out to be considering there likely won't be many online 3rd party games you can use that for or the quasi requirement to buy a SD card on top of all the other costs. So unless Nintendo does aggressive price cuts or manages to bring over the Pokemon/Yokai Watch/MonHun playerbases over without drastic losses (which I doubt considering above points, though we will have to see how much the respective playerbases are willing to fork out in the end)...
It is also important to remember that the leadership of the company is not the same as during Iwata's time. The current CEO worked for a bank for 27 years before joining Nintendo rather than Iwata who grew up with games and working on them, so don't expect the same compassion for games and gamers rather than pure maximum profit orientation from the top.