More or less. The Wii U is architecturally very similar to the Wii, just with a higher clockspeed, a couple of extra cores, more RAM and a better GPU; the Wii in turn is just an overclocked overspecced GameCube. It's possible, through a homebrew application, to load and run GameCube games directly on the WiiU.
If you're interested in this kind of thing, I'd highly recommend the architecture of consoles series of blog posts[1][2].
[1]: https://www.copetti.org/writings/consoles [2]: https://www.copetti.org/writings/consoles/wiiu/
But also it should not be needed at all. The switch has a older but somewhat "normal/standard" graphics API (and also support actually standard Graphics APIs, especially indi games and similar likely use that one).
My guess is that due to various factors Nintendo decided that it is _financially_ the best decision to extend the Switch lifetime and maybe skip the "follow up console" instead only bringing out the OLED Switch (or change the design of the follow up console).