I argue against using gens outside of discussions of succeeding models inside a company. But my answer is to you saying most websites classifying Switch as 8th gen. I don't know if most websites do, but that in itself is not a good reasoning at all, reasonings should be based on something else than 'others say it'. I personally think the whole categorization is futile.

EDIT: Best thing for generations is based on the time it was on market. That is generally aligning with how we outside of video games classify gens. For people for instance we have Gen X, Millenials, Zoomer, Gen α. But some Zoomers might have interests or character attributes, which align them more with Gen Xers with the same interests/characters. So the classification is purely time based, not on something else.

I agree that my reasoning isn't the best either. Hence the need of a discussion. And why do we need to categorize console "generations"?

Now we use to dismiss Nintendo. So when they use the term generations to separate specs capabilities instead of time, they will put most of the Nintendo systems as something that has passed its moment.

9th

For me it’s pretty simple. Everyone accepts that Wii & DS belong to the seventh gen and WiiU & 3DS belong to the eighth gen, right? So Switch, as the next in line, belongs to the ninth gen, and the successor to Switch belongs to the tenth gen.

As for why the classification is important, well it’s not really. But it’s handy to have an agreed-upon way to group things, especially because we’re all in the business of talking about video games — past, present, and future.

That's funny, because it leaves those that go against labeling Switch and its successor as a 9th and 10th gen consoles with such a convoluted reasoning.

It's really not that hard to grasp the idea of this cycle:

The big 3 each one releases a console, when we have the first replacement is when we start a new generation. Simple As That 

If Switch 2 releases in 2025, it will compete most of its time with PS6 and the next XBox, so it would be 10th generation. I'd always consider the generational subdivision to be based on broad timing and subsequent competition.

The situation wouldn't be much different from Mega Drive releasing some time before SNES (two years in Japan), or Xbox 360 before PS3 and Wii. I agree the Switch 1's placement due to WiiU's failure is a bit blurry because it spent its time more or less equally divided competing against PS4/XBox One and then against PS5/XBox Series. This doesn't matter much though, because even if you'd consider Switch 1 to be 8th Gen instead, then Nintendo just didn't have a 9th Gen console. Atari for example also isn't considered to have had a 4th Gen system with the 7200 being considered 3rd and the Jaguar 5th.

ColecoVision started 3rd in 1982.

Then in 1983 you have SEGA SG1000 (which is pretty much the same hardware as ColecoVision) and Nintendo Famicom (which was directly influenced by ColecoVision, as per designers).

Is power the defining factor?

Then GameCube and Wii, should be considered the same gen, same with Wii U and Switch. And Gameboy and Gameboy color should be considered different Gen. But I don't think people see it that way.

I just don't think power is the defining feature anymore. Not with games being scalable as they are to be played on all kind of different devices and PC specs. What about a Tablet or a Phone? Speaking of Gen whatever I think is something of the past and will become less relevant and in my opinion already is.

It's a hybrid.

A hybrid doesn't mean all Hybrids are the same.

A hybrid is a device that takes upon different aspects (Mobile and fixed home console) and combines them into one device... And often will have compromises or overriding dominant features.

The Sega Nomad from 1995 for example shares many similarities with the Nintendo Switch.
The Sega Nomad could play full home console (Genesis) games on the go, but also output to a TV.

It's still different from a Switch or a WiiU, but it was a Hybrid device.

Arguably, the Switch is more of a mobile handheld and the WiiU was more of a fixed home console, the WiiU sacrificed range, the Switch sacrifices power for mobility and battery life.

Obviously the WiiU was a market failure, so there was very little financial incentive for Nintendo to release a WiiU 2.0.

The Switch on the other hand is potentially set to be the best selling console of all time... So how do you follow that up? Reinvent the wheel with something different and hope it's a success? Or you take that current concept and refine it which has less risk financially?

Microsoft is likely positioned a little more optimally to push into the handheld market... They have Gamepass.

But also the Xbox Series S, which has a hardware technology base that can easily be made portable, so that could potentially skip the developer issue entirely that would allow Series S games to run natively.

Nintendo has attempted to have one device, multiple screens, this is probably the best way to grow your market in a market that is static in size.

Sony will be an interesting case, the PSP was an amazing handheld, the Vita just lacked support... And video games are getting more intensive to build and support, so it's unlikely to be viable to support multiple platforms going forwards, Nintendo even struggled to do it.

I just want Ray Tracing to be pushed in a big way. It's been a long time coming.

NES is 3rd Gen. Switch is 8th gen.

Remember the Switch may have released in 2017, but it's hardware is from 2015. - XBox One And Playstation 4 dropped in 2013.
A company can release more than 1 device per console generation... Or may even skip a generation.

Atari did it with the Atari 5200 which shared the generation with the 2600.

Playstation 4/Playstation 4 Pro and Xbox One/Xbox One X and Xbox Series S/Series X.

Probably a few more examples out there, but you get the idea.

We can't really go by "years" either... The Original Xbox only existed for 4 years, the Gameboy Advance was only around for 3 years before the DS came... Which really hazards back to my technology definition, console graphics technology tends to be a sort of "eb and flow" with the generations, significant leaps in graphics technology tends to coincide with a viable console successor.

Wikipedia is perfectly fine.

You can't exactly jump onto wikipedia and start injecting your own views and opinions into articles... That is, unless you have citations.
Which is this annoying little bit of "evidence" to support your articles in wikipedia.

Thus, check the citations in an article to ascertain the veracity of claims.