First, there's the role of hand drawn animation and how it developed early in the history of the medium. For all the time it lasted, how did it change, why, and what does that mean to the history of the medium? Why and how did computer animation gain dominance?
You can easily read on the history of hand drawn animation in the United States, but there's an important thing to talk about here. The fall of Mosfilm which produced puppet and cutout films, and how Soyuzmultfilm delayed the tradition within Russia, tending towards Disney-esque films only to break out of the Disney tradition within hand drawn animation and letting the other forms resume later. This effectively meant that hand drawn animation would be seen as the dominant medium around the globe, at least until the popularity of CGI.
Now that I've got that out of the way, I have to ask the question of the distinction between 3D and 2D CGI. 2D CGI is largely seen by its practitioners as developments of whatever medium they prefer, in spite of the fact that pixels are manipulated instead of cut paper or medium put down on paper. It is, the way I see it, a bunch of clever ways to stroke the hairs on a camel's back, ways to suggest a lot with very, very little though film and animation in general can be described in exactly the same way. The distinction between 2D and 3D CGI today, as far as I can succinctly describe it, seems to boil down to three things: computer modeling based on technical drawing, forward and inverse kinematics, and attempts to produce realistic shading. There's a fair amount of less realistic looking CGI coming out now, but doesn't it seem a bit too much like a clever joke based on a colloquialism?
So when did 2D computer animation become hand drawn animation, and how should a person distinguish between computer scanned imagery colored on the computer from imagery created entirely through the computer? What does it say about human culture that there are so many artforms that are in some manner expressed through the dancing of pixels on screen?
And doesn't it seem like the 'story first' mantra is being too commonly used by Pixar as a cheap way to dodge the issue? Where exactly are these brilliant storytellers? There's too much buddy formula, happy endings, and nostalgic abuses of old shorts. Cars hails back to late 40's Disney shorts, A Bug's Life hails back to Silly Symphonies, toys were the focus of an awful lot of 30's cartoons, Ratatouille plays off a tradition of mice and rats in cartoons, and The Incredibles has enough superhero cartoons preceding it. Finding Nemo was preceded by enough Hollywood short cartoons revolving around fish. WALL-E is a blatant exception, but it's basically Ben Burtt-isms for main characters in a fairly typical sci fi world. PIXAR films don't really get all that deep in my opinion. I think it's really just that the story keeps the audience distracted enough from the technology which the audience supposedly doesn't care for. There's an awful lot of talk about how PIXAR is occasionally willing to try out other mediums, but only rarely and for minor purposes.
We've lost track of something deeper here than the people throwing around the story mantra would have you believe. Hardly anybody really gives a damn about resolution, as the switch to digital technology has proven. And the moment you switch to a digital pixel display, hand drawn animation rendered in pixels is no better than 2D computer animation. It's what's being done that matters, the way things are being moved. It's the way a computer allows us to move things that we need to take into account, not the fact that a computer was used.
I don't believe that there's much a person does that can't eventually be mimicked by machine or that there's anything innately human that another person can't achieve similarly through technology. The moment you bring up a machine though, many traditionalists seem to completely lose appreciation for whatever is being made. I don't suspect that it's that something looks mathematical that most traditionalists despise, but that everything within the nuance of human expression can be interpreted mathematically.
Look at the general ways that things, generally characters, are moved within different mediums.
Stop motion relies on models adjusted frame by frame.
Hand drawn animation relies on a new drawing for each frame.
There's replacement modeling, which relies on a new model for every frame.
Cutouts rely on the exploration of a small number of parts in motion.
3D computer animation is essentially technical drawings reformulated by a computer and rendered over.
So what techniques can you use on the computer? Well, you could use all of them with the right software, but it doesn't seem to have become the norm. Computer animation isn't another medium anymore, it's a means to examine every medium and try out ideas, many of which can lead to new mediums outside of the computer. There's so many hand drawn animators and fans screaming at people deviating from using their standards inside of a computer when they hardly have a medium left anymore. It's all just red herring to keep people from realizing that there's very little left to hand drawn animation as a distinct technique in and of itself. There's a reason why hand drawn animators and fans keep rubbing our noses in tradition: tradition is almost all that's left of hand drawn animation.
I consider hand drawn animation with drawings scanned into the computer to be a thin exception from computer animation despite it's history preceding that of 2D computer animation for the public. Just take a look at SANDDE and Rhonda. These are helping to break the gap between drawing and modeling on the computer and thus forcing the question of what computer animation really means.
Who knows how 3D will blur the distinctions further, but it's time nonetheless, to reevaluate what constitutes hand drawn animation and computer animation. I say that anything animated from entirely within computer constraints is to be classified as computer animation and anybody toeing the line while maintaining an anti-technology stance is to be severely criticized.