Nintendo games dont appeal to modern gamers.

This generation 6 games have sold over 10 million, 16 have sold over 5 million and around 50 have sold over 1 million.

They are sooooooo out of touch.

Then care to explain how the Wii U is the slowest selling console ever? Nintendo games appeal to Nintendo fans and no one else. As evident by Wii U sales, there seem to not be many Nintendo fans...You really need to get past the "NINTENDO SOLD STUFF ITZ OK!" mantra because the quarterly losses from Nintendo clearly show there IS a problem. 

Poor Maketing

Name Confusion

Gamepad not attractive for many

Games drought

The games avaible for Wii U are fine, but many mainline games from Nintendo were lacking in its sytem. You should branch out your vision and stop looking only to Wii U hardware numbers, maybe you'll get over from the "Nintendo fans dying breed" mantra.

Edit: I don't know why I answer this, you could just read the OP.

While I don't think Switch games look ugly, I will point out that Breath of the Wild is 900p at 30fps and Splatoon 2 is 720p at 60fps. 

Give praise where it's due, but be honest about the points you're trying to push.

Name confusion is part of poor marketing, and do you have any evidence that the gamepad wasn't attractive to many? Also considering the Pro Controller for the Wii U was released, that shouldn't have been a roadblock to higher sales.

How is it that the games available for the Wii U are fine, but there was a games drought...?

What we CAN be certain of is that the Wii U has been the slowest selling console EVER and during its lifecycle, Nintendo posted its first ever quarterly losses. 

Here's some evidence that Nintendo fans are in short supply:

1) The low sales of the Wii U, a console that relied almost entirely on Nintendo IPs
2) Super Mario Galaxy sold 12 million units, with the sequel selling 8 million, yet on a console with a user base of over 80 million. If Mario is popular outside of the Nintendo fan base of ~10 million people, care to explain why such a small percent of the Wii userbase bought those games?
3) Low Wii U sales coincides with their lowest ever handheld sales

Also, ignoring the Wii which was a casual gamer success, here's the record of Nintendo console sales:

N64: 32 mill
GC: 21 mill
Wii U: 13 mill

Are you going to say that that trend is merely a coincidence?

Care to explain how they sold 80 million units of hardware & over 200 million units of 1st party software in the last 5 years? If they can do that just from "NINTENDO FANS!!!" than they will be fine. Saying Wii U is proof that only Nintendo fans buy Nintendo products is the equivalent of using Vita as proof that only Sony fans buy Playstation products.

You also dont seem to be up to date on Nintendo's fiscal results. This will be their 3rd consecutive year of posting an annual profit.

Your arguments could not be more ignorant.

Fine in quality, not in quantity. Try using reading interpretation

Too lazy to adress the rest of your post.

Aaand, why are we ignoring the Wii again? Ah, because it fits with your narrative. Gotcha.

Actually, point #2 proves that the Wii was a hit with casual gamers as several core IPs had an incredibly low percentage uptake on the Wii. Of course, if you want to pretend the Wii wasn't a hit with casual gamers (even Iwata acknowledged this fact), feel free to rewrite history #alternativefacts

The whole hardcore/casual thing is little more than bs marketing terms made up by the industry to dsicredit Wii's success and to separate gamers into demographics in a shallow attempt to analyze sales. The only thing that matters is gamers/consumers vs non gamers/consumers. Sure, Wii did well with the "casual" market, but plenty of core and lapsed gamers also liked the console. People bought the thing. Whether "casual" or not, their money is as good as anyone elses.

The big question is will Switch attract more gamers? Jury is out, though I think it will. You have games like 1,2 Switch and Arms for the mass market, Bomberman and Tetris for the lapsed gamer, and Xenoblade, Mario, and Zelda for the core Nintendo gamer. You also have the appeal of the convenience of being a handheld, which could bring in a bigger audience.

Wii U mainly just appealed to the hardcore Nintendo fans. It was a Gamecube disguised as a Wii, with a crappy controller to boot and an overall weak library. I don't see any of these traits with the Switch.