The Series S/X is copying a trend that the market is used to. Almost everyone has a cell phone and is aware of the iPhone S/X's. S means newer than base, X means newer than base and more powerful too. This is just common knowledge now.

What is named with a U? Who even does that? Wii U? It's nonsense!

Name and marketing like others have already stated is the main issue that caused it to fail.

The biggest shame in all this? For me the hardware and features where actually pretty good, i'd argue better than Switch. Some of the freedom that we had on WiiU with how you back up files has been taken away with the Switch.

Because software is just one component in selling hardware. The hardware itself has to be just as compelling, captivating, and cool as the software that's on it. And the Wii U was the furthest thing from any of those adjectives.

Final Fantasy VII, Gran Turismo, and Crash Bandicoot wouldn't have sold nearly as much if the PS1 was a piece a crap.
The library of games on the Wii U, as great as those games were like Splatoon, Smash 4, Mario Maker, 3D World, Hyrule Warriors, Mario Kart 8 and Bayonetta 2 just to name a few, were few and far between, and to make matters worse, the console just sucked.
Marketing and naming certainly didn't help,
Even if it was called the Wii 2 and there was no confusion about what the hardware was, people were over the Wii concept by that point. The majority of people that made the Wii a grand slam were the extremely casual gamers that left in droves because they were content with just having that one console and half an hour of Wii Sports or Wii Fit and that was it. And the dedicated gamers preferred the HD twins with a more traditional setup over the underpowered console with a motion control gimmick.

Thats because the WiiU was a Wii system. Basically like a Wii Pro with a new controller. Its all part of the Wii family hence the name.

because the logic of "all that matters are the games" is not true for most of the people who buy consoles, and the only people you ever see spouting that are the "hardcore" who pay attention to video game forums and video game news online. the same people who buy many games per year at full price on day one, and will buy a console just to play exclusives that they love. they don't need to be convinced to buy a system, why would they care about what it does? all they know is it will give them the games they love and that's enough for them to put up with any other bullshit that comes with it.

if all that mattered was exclusives then why has Spider-Man "only" sold 20m on the PS4, a console that sold 100m+. why has Animal Crossing: New Horizons "only" sold 26m on a console that so far has a userbase of 70m+. it's because most of the people who buy consoles don't buy them with the intention of buying every exclusive or big game in sight like the vocal minority of "hardcore" do. if anything exclusives are the exact opposite of what they'd want, they're not gonna buy a console just to play one game. instead they're gonna want something they can use to occasionally play FIfa or Call of Duty with their friends on, perhaps also use as a multimedia or entertainment hub to watch Netflix on, and if any other games come out that peak their interest such as an exclusive maybe they'll buy that as a bonus and they're perfectly fine with that.

exclusives matter of course and are a big factor in swaying interest but at the end of the day they are just one factor, and if the actual hardware itself doesn't offer anything of value or is desirable in any way outside of those then they can only go so far, and the Wii U is the epitome of that. because aside from those great games, what else did it offer? it didn't have many of the features the new consoles that came out a year after it had, it was slow as fuck, hardly had any storage, the naming and marketing was so god awful that it turned most people away and many didn't even know it was a new system, and its defining aspect which was the Wii U gamepad that could have set it apart from anything else went severely under utilized because 99% of developers, including Nintendo, didn't even know what to do with it. it offered nothing except being a lesser variant of what the other consoles were doing significantly better and offering way more. the people who bought it are the ones who would have already done so for the games, everyone else was given no reason to want to.

normally when a system is failing companies will at least try to find ways to reduce price or make them more enticing, but with the Wii U there was nothing Nintendo could do because the gamepad was an anchor that dragged down the system for its entire lifespan that they couldn't get out of. I love Nintendo to bits and think they are the best in the industry, and I felt for them during the dark Wii U times, but I legitimately believe everything about the Wii U was Nintendo at their worst decision making possible all at once, and one they only have themselves to blame for. 

this is why the Switch is an incredible success because it offers an inherently incredible value from just having the system itself which is being able to be taken anywhere and used anywhere. knowing that you can get Super Mario Odyssey, Breath of the Wild, etc and all these huge games is of course an influencing factor that will sway people to want it, but the system itself being desirable and what it offers is just as important as that. 

The hardware at least needed to be desirable in term of design and features and not a huge clusterfuck like WiiU

A few points of WiiU failures
-Confusing console Naming that most people thought it was a Wii peripheral instead of a brand new console that they had to address it later on in their marketing campaign
-Bad hardware Design with a big ass controller as the main focus as Nintendo themselves unable to utilize it fully
-Bad marketing that was clearly targeting the casual demographics that had abandoned Nintendo for Smart Device
-Software drought as HD development time caught their ass off guard
-Underpowered console without a good gimmick

You need to understand that for the average Joe, the Wii U library kinda monumentally sucks ass.

3 things. 1 software sells hardware. Wiiu library is piss poor. U have to have quantity and quality to compete. Not just 1 or the other. 2 software sells NORMAL hardware. If a gimmick is being shoved in ur face as the selling point, then u have to look around it to see the games. 3 for software to sell, it needs enough power to run on the console. 10dos insistance on cost cutting to sell gimmicks instead will always be a risky move for the health of their game libraries. No one I knew at the time had any confidence wiiu would keep up w the ps/box that released the following year in terms of power to run 3rd party games.

As a long time Nintendo fan I would say price. I get that the software will always be good but at a certain price it felt like Nintendo was riping us off. The Wii u was not worth the asking price even if the games themselves where.

And I was one of thouse who till the near end always thought nintndo was gona turn arpund and remove the tablet and drop $100. I guess people like me ended up looking like fools here.

Edit.  I think this quote fits perfectly here by who ever said it.   "There's no such thing as a bad product, just a bad price"

Coming from my own experience....I legitimately thought " WiiU" was Nintendo's answer to the UDraw tablet from ubisoft. It wasn't until I did research and understood that it was a new console that I was excited (though limited funds kept me from purchasing).

Anyway...if a big gamer who has owned dozens of systems was confused, I couldn't imagine joe shmoe