Wii U failed due to these factors: Poor marketing, lack of third party games, and droughts.

The Wii U was a great console, the Dreamcast of it's generation in many ways 

While exclusives matter, they don't matter as much as people make them out to be. Some 80% of sales on the Xbox and PlayStation brands are 3rd party titles. Out of the top 10 best-selling games, only 1 game is an exclusive on each console last time I checked.

Teh warz neva endz.

This isn't a relevant example for Nintendo consoles 

I don't see why we can't take anything from it. After all, they're targeting a lot of the same people. People who play games on dedicated gaming systems.

While Nintendo doesn't conform to much of what the rest of the industry is doing, it's still quite telling that their most successful home console is one that just happened to capture lightning in a bottle despite being in the business for the longest of time. When 3rd parties shifted to Sony after the first PlayStation.... Well... Yeah.

Wii Us good exclusives took some time to release, and then they dried up just as fast. Switch has had good exclusives since day 1 with TLOZ Breath of the Wild and Nintendo is trying to keep it churning with Super Mario Odyssey and Super Smash Bros.

Consider this. Wii U's promised system seller didn't release until the Switch was out, of course I am talking about Breath of the Wild. Nintendo's SW output during the Wii U was pathetic compared to the Wii even from the start with Nintendo's full support.

Exclusives do matter a lot, but they're not everything. Wii U had many failures: It was expensive for what it was, had a complex selling point that even Nintendo struggled to showcase, poor marketing and name, and so on. Not to mention most of Wii U's exclusives lacked ambition or weren't what people expected. It never had an exclusive Zelda, it never had a Metroid game, it had the worst 3D Mario, the same old "New" 2D Mario as a main system seller during its first year, a 2.5D DK when people expected a 3D one at that point, Smash released first on 3DS which disrupted its sales potential on Wii U, and so on. The highlight of the system was Mario Kart 8, which was an ambitous game (it had great graphics, a new gameplay concept, amazing tracks, characters from other series, great DLCs, etc). Coincidentally, it was the best selling game of the system.

Meanwhile, Switch is almost the opposite: Great value for what it is (a hybrid of home console and handheld), an easy to sell concept, great marketing, an easy to get name and ambitious/high quality exclusives.

Well you were talking about software - "Some 80% of sales on the Xbox and PlayStation brands are 3rd party titles. Out of the top 10 best-selling games, only 1 game is an exclusive on each console last time I checked.", in which case your example is literally not relevant to Nintendo in the slightest, because pretty much every Nintendo console had Nintendo games selling the best - even the ones that got good third party. 

I will agree to some extent with your furthered explanation, although it's not really due to a loss of the power of exclusives. I think Wii sold a lot because it had hardware that was appealing to a mass audience due to it's uniqueness, in the same way the Switch does currently. Of course the Wii's lasting appeal was (or most likely will be) much shorter than the Switch's, but the biggest problem is that Nintendo consoles that weren't handhelds were offering substandard hardware to play games with. It's not so much that they were lacking in power (the N64 and Gamecube clearly weren't), but there were a lot of caveats that weren't outweighed by a different type of play. Of course the Switch is a handheld, and Nintendo handhelds always get more third party support - but I doubt the third party that the Switch is getting is affecting the sales as much as the exclusives are (and the third party games that sell Nintendo handhelds tend to be heavily Japanese oriented anyways). 

I think the winning ticket for Nintendo is exclusives and unique catches - one can not function without the other, which is why I don't ultimately agree that exclusives have lost their power on Nintendo consoles. Without great games, Switch would sell, but it wouldn't be selling nearly as great as it is. 

Wii U was a dumpster fire as a system and had very few games that were of high praise
Bayonetta 2
Mario kart 8
Smash bros
Splatoon
Donkey kong
Yoshi
Super mario bros
Xenoblade X
Zelda botw
Pokken
But other than that there was nothing else but shovelware and bad multiplats

Wii U didn’t get Breath Of The Wild until the end of its life and also no mainline Pokémon or Animal Crossing game.

The name itself was a major fail. Had they named it the Wii 2 it would have sold way better.

The U part was so dumb and confusing. Most consumer thought it’s a mild upgrade or just a revision of the Wii not worth buying.