Non-Photorealistic Rendering
Artists explore where the mainstream is not. That's been true for as long as we've had artists exploring. Early art worked to develop techniques that capture reality the way we see them with our eyes. And once tools and techniques were perfected for realistic renditions, artists like Picasso and Dali went off to explore art that has no ambition to be realistic.
This evergreen cycle is happening in computer graphics. Early computer graphics were primitive cartoony blocks but eventually evolved into realistic-looking visuals. We're now to the point where computer generated visual effects can be seamlessly integrated into camera footage and the audience couldn't tell what was real and what was not. But now that every CGI film looks photorealistic, how does one stand out? The answer is to move away from photorealism and develop novel non-photorealistic rendering techniques.
I saw this in Spider-Man: Into the Spider-Verse, and again in The Mitchells vs. the Machines. I was not surprised that some of the same people were behind both films. Each of these films had their own look, distinct from each other and far from other computer animated films. I remember thinking "this might be interesting to learn more about" and put it in the back of my mind. So when this clip came up as recommended by YouTube, I had to click play and watch it. I'm glad I did.
From this video I learned that the Spider-Verse people weren't even sure if audience would accept or reject their non-conformity to standards set by computer animation pioneer Pixar. That is, until the first teaser trailer was released and received positively to boost their confidence in their work.

I also learned that they were created via rendering pipelines that have additional stylization passes tacked on to the end of existing photorealistic rendering. However, I don't know if that's necessarily a requirement for future exploration in this field, it seems like there'd be room for exploring pipelines that skip some of the photorealistic aspects, but I don't really know enough to make educated guesses. This is a complex melding of technology and art. It takes some unique talent and experience to pull off. Which is why it made sense (in hindsight) that entire companies exist to consult for non-realistic rendering, with Lollipop Shaders the representative in this video.
As I'm no aspiring filmmaker, I doubt I'll get anywhere near there, but what about video game engines like Unity 3D? I was curious if anyone has explored applying similar techniques to the Unity rendering pipeline. I looked on Unity's Asset Store under the category of VFX / Shaders / Fullscreen & Camera Effects. And indeed, there were several offerings. In the vein of Spider-Verse I found a comic book shader. Painterly is more like Mitchells but not in the same way. Shader programmer flockaroo has several art styles on offer, from "notebook drawings" to "Van Gogh". If I'm ever interested in doing something in Unity and want to avoid the look of default shaders, I have options to buy versus developing my own.