I think animation could have a dedicated section apart from 2D or 3D. The principles hold true through whatever medium and however many dimensions you use, right? So, animation could just be in "Art".
Or, it could have a dedicated thread in each section (2D animation and 3D animation), like the pixel art thread does in 2D. Like, there's not really any reason to have a Pixel Art sub-forum instead of the current single thread for it, even though there could be a ton to talk about in regards to pixel art in particular.