In the industry there used to be a big split between cg animation and vfx work. Different pipelines, different organisation of crew. Now a lot of vfx films have whole sequences of full cg shots, so it's not so different to making animation.
It's why I gave up on marvel. I think superhero content is better suited to cartoon format. DC Animation has the best hero content imo.
I really dislike superhero movies in general, especially this non-stop Marvel/DC stuff, and a primary reason for that is the way they tend to go in and out of live action and animation. There's an uncanny valley thing that happens in that transition, and you can obviously still tell that large portions of the live action stuff is shot on a greenscreen. It all looks fake as a result. My suspension of disbelief is shattered.
But when a movie like this admits it's animated, things improve a lot. I watched the first Spiderverse movie the other day with my kid, and I absolutely loved the art style. I had other problems with the movie, but the visual style was not one of them. I wish there were more animated movies targeting older audiences with unique art direction like that.
It is getting heavier and heavier but I don't think we'll see CG dialogue scenes or close ups of humans for a long time due to the uncanny valley factor. Fully CG animated films are still heavily stylised to avoid it.
I'm just waiting til the day that a fully AI generated feature film gets released.
This is actually discussed on the live-action animated film Wikipedia page.
Since the late 1990s, some films have included large amounts of photorealistic computer animation alongside live-action filmmaking, such as the Star Wars prequels, The Lord of the Rings trilogy and the Avatar franchise. These films are generally not considered animated due to the realism of the animation and the use of motion-capture performances, which are extensively based on live-action performances by implementing actors' movements and facial expressions into their characters. Roger Ebert said that "in my mind, it isn't animation, unless it looks like animation."
Related note: I'm quite nostalgic for the mid-20th century live-action animation trend (even more so than the late-20th century puppet trend). If the characters are going to look fake regardless, the animated ones are way more expressive and, well, animated.
There's also a lot of difference in mocap vs traditional animation. When characters are animated they follow certain principles that aren't realistic but result in pleasant and entertaining movement. Real humans and creatures don't behave this way.
So when animators are working on live action films they have to carefully balance the adherence to these principles with the realism of the scene.
There's obviously liberties taken (the mocap data is always cleaned up before being applied to a character) but think of the difference between an explosion in a Michael Bay film vs one caught on someone's camera in real life.
Sounds like you're unfamiliar with the widespread use and long history of rotoscoping in traditional cell animation. Motion Capture is just rotoscoping with modern tools.
I think the better question is what purpose is served by trying to categorize movies into "cartoon" movies and "not cartoon movies"?
Toy Story is a CG movie and has more nuance, character development, and purpose than say, the live action film Hackers, and so does Who Framed Roger Rabbit, which is a mix of live action, special effects, and traditional hand animation, so what purpose is served by chunking them up based on which one used film editing / splicing, which one used stop motion, which one was traditionally animated, which one used CG, and which one had some blend of the above?
That's actually a petty definable line between animation and live action, but some action films have enough animation to be considered a mix of the twon in a least some cases.