3D animations require you to model out everything, then use different methods such as armature and object positioning keyframes to create movement, while 2D requires you to draw it out frame by frame. Sure, some things can be copy and pasted, but when a character change position you have to draw them all over again. It just seems so tedious
note: I do 3D animating but never touched 2D. How do I get started with 2D?