I feel like it's boring, but I'm also generally of the opinion that it was extremely necessary to make a break from the visual identity of the Wii/DSi/3DS/Wii U. Nothing says "this is a fresh start for Nintendo!" more than having a menu and atmosphere that is basically the same as those consoles, especially considering each one says something about what that console in particular is going for.
The Wii's links into the console's design as an extension of the TV by mimicking the visual language of various TV things, like the clock being of a similar design to the one used by NHK at the time, the news channel being essentially visually identical to Japanese news broadcasts of the time, the apps being referred to as channels and being designed around being small TV screens (complete with static), and the music in the various apps is similar to stuff from Japanese TV or shops. (There's a really interesting article about it
here, and I really recommend reading it!) It's trying to be something accessible and something familiar to people who haven't really played games before, which is in general the Wii's entire MO.
The DSi's menu overhauls the DS OS from something arguably more generic (it's very reminiscent of
the PSone's menu) to something more tied in with the Wii's entire aesthetic to make the fact that they're meant to be somewhat simpatico as two products from the same company, and you can connect them to each other in certain games (including LGTTC, which came out around about the same time as the DSi in Japan and is at least partially marketed as "you can move from handheld AC to console AC"). In addition, it's capitalising on the idea that a handheld is a more personal experience than a home console, so you've got whatever photos the user's taken with the newly-added camera on shuffle on the top screen and you've got a music app so that you can put in an SD card into the newly-added loaded with music on and use as a kind of Gamer iPod.
The 3DS is largely an evolution of the DSi's menu and is largely working on the same kind of design principles, just slightly different. It's got more pre-loaded apps on it compared to the DSi, utilising the 3D cameras for AR games, and utilising the system's rest mode ability and portability for Streetpass, which allows people to collect pieces of little 3D pictures or play games with your Miis. Roughly halfway through the 3DS's lifespan, the New 3DS came out, and that had interchangeable cover plates and was
even more focussed on being "your" console, coinciding with the launch of themes matching the designs of the cover plates and Nintendo Badge Arcade, so you could win little badges to further customise your own console and make it your own thing. It's not a massive revolution, but imo it didn't need to be.
The Wii U's aesthetic is also an evolution of the Wii's aesthetic, but in a less successful way than the 3DS. In a nod to the fact there's a tablet controller, there's also a hefty dollop of iPad-style design language in the mix this time, from the move from TV-style icons to glass-style ones, to the fact that it's got its own Mii-based social media network (RIP Miiverse). However, in a lot of ways it feels like a downgrade. A lot of the apps on the Wii don't really have equivalents there, not helped by the fact that the development for pre-loaded software ended up turning into Game + Wario, one of the less popular games in the WarioWare series. There's more variety of music on the system, but in general it's less iconic than the Wii's (and in some cases it's just straight-up annoying, like the
settings music). It doesn't really feel as intuitive as the Wii's, as its design language is generally kind of split between TV and tablet, and its message is as confused as basically all of the Wii U's advertising. It's also
painfully slow. I think the move to the hyper-minimal Switch OS is at least partially a reaction to the fact that even after a major system update early on in the console's lifespan, you're waiting around forever for anything to actually happen.
The Switch's general aesthetic is imo, largely based around it easy to use and light to use. The designers of it
cited the NES as being an inspiration, where you boot it up and go straight into playing your games, and unlike the PS5 (which of course, Has No Games), the games are very much the star of the show here. The most prominent thing on the menu is the game icons, which utilise (more often than not) the game's boxart. There's some icons for the news app, the eShop, gallery and settings beneath that in a clear location, a nod to the design language of TV with another NHK (circa 2017)-style clock, but aside from that, just solid white or grey. It's fully embracing tablet design language, but given the Switch is a slightly bespoke version of a tablet anyway, it's very in keeping with the same kind of principles the Wii was using a decade before.
But yeah, it's more boring than before. Part of that is due to the fact that glossy Frutiger Aero skeuomorphism isn't really
in anymore, and minimalism has been the in word in graphic design for over a decade now (for lots of reasons, from "massive global recession causing many companies to cheap the hell out on graphic design in several ways", to "Jony Ive redesigning iOS in 2013", to "the rise of smart devices necessitating flexible branding that's recognisable at any size, from icons to billboards"), part of it is the fact that it probably wasn't going to get themes like the 3DS (again, I feel like they only did them with the 3DS as a tie-in with the New 3DS and feel like Nintendo are exactly the kind of company to only do them for stuff like that, tbh) and due to the size, lack of stuff like cameras and microphones and its hybrid nature there's nothing like Streetpass or streaming apps, you
have lost some of that Quirky, But With Purpose Nintendo character. But it's neither completely without quirk or purpose, and I'd rather that than Nintendo continuing to do the same thing they did before because it's A Thing Nintendo Does, Because They're Nintendo. It'd have been more visually interesting, maybe... but it'd have felt dated and wouldn't really have felt like the symbolic break from the Wii/DS family the Switch is.
Do I think it's going to change with the upcoming successor? Not really. I think it's going to be utilising the same kind of design principles that the Switch uses, if maybe using something slightly less mid-2010s like
neuomorphism. There's inevitably going to be more oomph in terms of power so there's the potential to maybe do something a little flashier, but at the same time, this could affect the system's overall performance and again, I think they're bigger on letting the games convey the Nintendo personality more than they are the menu... and in the end, isn't that the most important thing?