Nowdays that's no longer the case. We arent getting those massive graphical jumps, just incrimental upgrades that it can be hard to tell what can and can not run on the current system (Heck, we had so many comments of people thinking Tears of the Kingdom looked too good to run on Switch). The games can't speak for themselves anymore so Nintendo has to find other ways to communicate that "this is the next gen"
They are obviously not going to market this new system with graphical differences alone. It would be in conjunction with a console redesign, new name, marketing 4K capability and extra features, and emphasizing the exclusivity of new games. And even then I think there will be a striking difference in the graphical fidelity of a new 3D Mario. In the event that someone is genuinely confused and think Mario Universe is running on a current Switch, they would find out eventually as the only handheld footage or physical demo of Mario Universe would show it running on the new tablet, and the boxart would only feature the Switch Super / 2 logo. Would '2' be the most clear choice? Yes. But they are not dead in the water with some alternative naming. Even the GBA, with its obvious power leap, still made sure to be distinct in appearance and slam a 'Only For GBA' on its boxart to make it extra clear.
Wii U has the issue presenting itself in such a way that it looks and sounds like an extension to the console rather than a new console on its own, both in name and how it was advertised. If it was called "Wii 2" or "Nintendo Universe" or somethin, a lot more people would've gotten the point that its a shiny new nintendo.
The point is not to just make it clear it's a new console and attempt to avoid brand confusion entirely. Giving it an entirely new name like 'Flip' or whatever would be entirely abandoning the recognition and appeal of this name specifically. Nintendo did not choose this name solely to distance themselves from the Wii U. It means something in relation to the console's capabilities and is an accessible word to write and speak, while having a 'cuteness' factor. People know now for six years what the Switch is and what it can do. They are more likely to buy a new console in that line because of it. Introducing a new console with a different name that does the exact same thing would just invite confusion and necessitate building that brand up from scratch.
It worked for the DS because of having significant differentiation from the Game Boy, and because it was worthwhile to distance themselves from the Game Boy brand which was 'gendered' vs the more 'neutral' DS. And even then it was positioned as a third-pillar initially because of the Game Boy's popularity. They could have easily given the GBA a different name like Super Pocket Pal and I'm sure they considered it but realized it'd be better to coast off their success.
Its also worth noting that there has never been a nintendo console that has continued a brand name and outsold the previous generation. They still sold decently outside of the Wii U don't get me wrong, but nintendo attracts a much more "casual/family" market than the other 2 major console companies, and those people would be more likely to be confused by something like "Super Switch"
I don't think it matters to them as long as it still sells well. And I remain unconvinced that simply having a name like 'Super Switch' will confuse. If they named it that and it looked identical to the current Switch and the logo and boxart was poorly designed without emphasis on the Super part, sure. The name is only one part of the marketing, as you said, the Wii U projects itself as some kind of accessory and didn't do enough to differentiate itself.
The "Nintendo" already carries the brand name enough in the same way "Playstation" does for the sony consoles. If valve or lenovo released the "Switch" instead not many people would've cared for it because its not "Nintendo"
Yes, there is inherent appeal in the 'Nintendo' name. But Nintendo designing a Switch-like console and ending up giving it a different name is just giving themselves more work. There's a risk-benefit analysis here, and I think riding on the success of an existing name offers a lot more benefits. If the Switch brand stops being popular then by all means, name the next hybrid console something else. Otherwise I see no good reason to change it.
And if the concern is minimizing brand confusion, '2' is right there. I don't think it makes Nintendo uncreative to go with 2. The important thing is what comes before the '2' - 'Switch'.
In all likelihood it'll be something completely different that captures the essence of the concept of the machine. I don't think it's going to just be "Switch but better", there will probably be something related to AR or AI or something else.
I don't think this is likely. The Switch brand is flexible and they've already delivered AR games. They can easily define 'AR' as simply another function of the Switch like handheld, tabletop and docked. I'm not sure what could be done with AI to make the console so different. When Nintendo changed brands in the past there was some justification, even if the reason was 'people aren't into this brand anymore' or 'the name is getting clunky and unappealing' (e.g. N64 instead of NES 64 and GameCube instead of N128). I expect future Nintendo hardware that doesn't Switch like a standalone VR or AR headset to be named differently, of course.
It kind of feels like I'm the odd one out here. The Switch name is associated with a console that packs so many different features and types of games that I'm not sure there is any meaningful addition to justify changing the name. The name itself is neutral, easy to say, and clear, and it casts a wide net with no specific connotations other than 'hybrid console gaming with extras'. The only good reasons I can think of is if a future primary Nintendo console either doesn't Switch (a stupid decision) - or simply, if the Switch brand loses popularity. Nintendo has course corrected on so many decisions from the Wii U that I don't think risking this is worth it for them. While names are partly a creative decision, they want to make money at the end of the day.