3D animation is incredibly difficult. Why would 2D be harder? Look at animated TV. How much of it is animated in 2D? Family Guy, The Simpsons, Futurama, King of the Hill, almost any Adult Swim show (Robot Chicken doesn't count, it's stop-motion), et cetera. And how many 3D-animated TV shows do you know? Clone Wars ... um ... yeah. Not to say that Futurama and occasionally Simpsons don't use 3D animation, but it's mostly 2D.

I use TV as an example because of the volume of work they have to do each year - think of that, and think of us doing 3 two-hour movies. We do want to finish this in our lifetimes.

I also room with an animation student. Trust me, it would be a lot easier to do 2D animation than 3D.