Strange though that people want to separate so much these two machines, they have nearly same capacities, same games, same size in hand, main concept is the same except that one is limited to 12 meters, the other one is infinite distance from dock. Games of the WiiU were all ported to Switch, Nintendo has proposed the "retro compatibility" where you pay two times full price a same game, and you all decided to deny this and call it "9th gen" instead.

Wii is a 7th Generation console. Wii U is the direct successor to Wii and the first console of the 8th generation. 3DS is the first dedicated handheld of its generation as a direct successor to DS. The switch is a successor not to just Wii U but also 3DS. The switch is not just a successor to Wii U or 3DS but Nintendo's entire console and handheld divisions. Merging the two departments internally. That merge gave us the Switch. The Nintendo Switch in both hardware/internal structure of Nintendo HQ and marketing. It is a 1ST GENERATION Hybrid Nintendo System. Period.

I don't see why this is difficult to grasp.  Next console = next generation.  It's that simple.

I'm inclined to believe that you actually do "get it".  You simply don't agree.  It's not hard to understand though.

Wii U was a 8th generation console.
Switch is the successor to the Wii U.
Therefore Switch is a 9th generation console.

Nintendo itself has long been clear they are in no way actually competing against the other console twins.

And Switch actually is a rebranded NVIDIA Shield (launched same year as PS4) with low power handheld mode.
Why would Shield's hardware generation change just because it's rebranded under Nintendo?

I see it more like a 8th gen console

Just like I see Game Boy as part of the same generation as SNES, even if outlived it and survived to as far as the Game Cube release

Switch will be similar. It will outlive most of 9th gen, and then Nintendo will "start" 10th gen, just like 3DS started 8th gen being released 2 years before PS4/Xbone

As the guy who made the charts (with the input of the VGC team) the idea behind it is to present the information that is interesting to compare.

Seeing how PS5 and XBS will fare against the Switch is interesting to follow and they are all the "current" consoles of the big 3.
It's also very interesting to see how Switch is catching up to PS4 so a graph comparing PS4, XBO and Switch is relevant.
Wii U was kinda left out by this so it made sense to include it in the Gen 8 graph.

NVIDIA Shield was 9th Generation even if nobody realized it at the time and it was weaker than PS4 released a few months later. /s

Seriously, at least VGChartz isn't trying to force things into "gen" model, with NS displayed in both current and lastgen tables.

Honestly, I think a front page showing all of that together makes the most sense, especially since PS4/XO is still on sale and relevant.
Not sure how many years that will continue, but since NS overlaps both I think it makes sense to retain all of them until NS ends.
And I think that makes sense to have all of PS4/PS4/XO/XS/NS/3DS in front page sales total table, because they all are in weekly #s.
(albeit it seems likely Nintendo will drop 3DS completely sooner or later at which point it shouldn't need to be in any current table/#s)

The idea of generations really only holds up well if appliedto one manufacturer. The PS4 was the next machine after the PS3, so a new generation. The WiiU was the next machine after the Wii, so it is a new generation. The 3DS is the next gen after the DS. You get the idea.

The moment you try to fit machines of different companies into one distinct generation and define overarching gens independent of manufacturers, you get into trouble. Yes, sometimes the release schedules somewhat line up, as different consoles tend to compete with each other. But that doesn't always work like that.

The proponents of clear gens tend to ignore 1st and 2nd gen and the lost gen. Because back then the lines weren't as clear cut. But even later some machines didn't line up as well. NES released in different regions at wildly different times. It released in europe more than 3 years later than in japan and only about 4 years before Super Famicom (SNES) released in Japan. So where does it belong? Where does the Dreamcast belong? How about the long tail of sales of the PS2?

The Switch is the successor to both the 3DS and the WiiU, and as handheld and stationary console already were not aligned, it was clear it wouldn't fit neatly into both timelines. As it is, Switch released right on schedule for a 3DS successor, but the life of the WiiU was cut short. A decision that was probably made easier for Nintendo, as the WiiU wasn't all that successful.

As I said before, competition made release schedules line up a bit. But Nintendo started at least since the Wii to diverge in their market approach. It is not like Nintendo isn't in competition with Sony and MS at all, but for the most part they doesn't affect each other *that* much. PS4 sold like it sold before as Switch released. Switch kept on selling as the PS5 released. That also makes it easier for the Sony gens and the Nintendo gens to not be aligned. Switch either reaches customers that aren't interested in Sony or MS offerings at all, but also customeras who happily purchase both. MS and Sony on the other hand are very well competing for the same market. That may change, with the increased focus of MS on Gamepass, and maybe in the future their schedules will also diverge to each other more.

An word about people that think gens are about tech: look at the history of consoles, especially older ones and see how wrong that assumption is. The only constant is, that the next machine of the same manufacturer will be a progress in technology.

So TL;DR: don't put your eggs stubbornly into the idea of defined gens independent of manufacturers. In reality the gens of different manufacturers only sometimes line up neatly.

As the Switch is so similar in concept and tech to the WiiU, that must be the reason it does sell so similar.

That is why the Switch Lite sells so much more than the hybrid model that includes a costly connection to TV handheld gamers don't need.

And this must be the reason the Switch sell as well as the NVIDIA Shield did.

"But Mnementh, Switch sells because it has a Nintendo logo on the package."

As did the WiiU.