I dont use AI for image generation so I dont know how possible this is, but why not generate a 3D model for blender to ingest, then grab 2D frames from the model for the animation?

Because, uh, literally everything. But the main reason is that modeling is actually the easy (easiest) part of the workflow. Rigging/animating/rendering in the 2D style you want are bigger hurdles. And SOTA AIs don't even do modeling that well.