The 3DS did not explode in popularity like the DS, but it's still very popular and sold and sells well.
Those "gimmicks" are also the reason the why PlayStation kicked their ass for like 20 years now. Don't get me wrong they should try something new but at the same time if it doesn't work they need something to fall back on and that has been lacking from them for a long time now.
Except the GameCube had far more power than the PS2 and that was like 15 years ago. Similarly, the N64 could pull off amazing things and stay on par with disc consoles, yet it lived mostly thanks to its first party line up of timeless masterpieces.
On the other hand, a good chunk of their consoles with gimmicks printed money (3DS, DS, Wii).
What would Nintendo gain from making a powerful system like what they did with the GameCube, nowdays? Losing to Sony again? Become an obsolete computer?
Horsepower does not sell a console. It's price, advertisement, piracy and word of mouth that do.
A lot of high selling consoles (PlayStation 1&2, Nintendo DS, Wii) had good advertising, were relatively cheap and could all be pirated easily.
Here in Italy, videogames took off with the PS1, and all the kids I knew had loads of pirated games.
Not to mention, PlayStations were never the most powerful consoles of their gens (not sure about 3 and 4), yet they still printed money.