I can't say I've seen many people hating on the 3DS recently, but the reason people give Nintendo a hard time is because they've done a lot of dumb trout. The Wii was a titanic commercial success but a lot of people regard it (rightly or wrongly) as having hurt video games as a whole. What's less arguable is that Nintendo's efforts with the WiiU have been a categorical disaster. Their online setup would have been decent a decade ago, these days it's a bad joke. The company is hemorrhaging money and has little on the horizon to help them, aside from Smash and Mario Kart 8, but given past WiiU form I doubt those will move many systems.

They're also the quintessential Japanese company, so junior members can't tell Iwata that anything is wrong and the higher-ups aren't going anywhere anytime soon. Plus if criticism comes from abroad Nintendo's response is "Hahaha foolish Gaijin, they believe they know better than us!" and they carry right on assuming the West will kiss Nintendo's ass and call it ice cream.

Nintendo fundamentally failed to grasp why the Wii was a success and what implications that had for them. It was an absolutely brilliantly marketed console that brought in unbelievable numbers of people who previously would never have been considered major video game demographics. The flip side of that is - and I'll toot my own horn and point out that I was saying this years and years ago - that these people are not serious or hardcore gamers. I don't mean that as an insult or anything, it's just a facet of their behavior as consumers. A Wii is a thing they bought because they liked that particular product, because the Wii specifically had stuff they wanted. We're used to the console cycle where we get new systems every few years, but to Soccer Mom and Random Grandma they've got a Wii, why would they want or need anything else? And they have no more loyalty to Nintendo than they do to whoever made their TV anyway, these are not people who will go out and buy a Nintendo product because of the name. Or for that matter people who will buy a console of any kind because in the future it will have a worthwhile library.

Nintendo assumed all these new customers would just naturally upgrade to the WiiU because that's what everyone else has done since the NES days, whereas that's not the case at all. Also not helped by the name, which is pretty much a total disaster that, to the layperson, gives no information about what the product actually is.

e; Also as Mr. Shauna points out the WiiU can barely match last generation's power, and Nintendo is notorious for being very unhelpful towards 3rd party devs. They have a very strong attitude that others should be honored to make games for Nintendo systems, and have never made the effort to court others or ensure consoles are convenient for them. Some have been, but it's by coincidence rather than design, and the WiiU certainly isn't one people like developing for. Between the power shortfall, development difficulty, and the lack of customers nobody's much interested in porting games to the WiiU.