problem is the original ldraw geometry, it's low poly, with geometry not optimized for animation.
when you rig a model you would have to add additional loops where bones are..
ie if you want a leg to bend at the knees, you would add loops and weight bones accordingly.
not to mentioned unnecessary polygons. ie, logo on torso is geometry, when a texture would work much better
if you would like to do a lego movie animation, I am sure unedited ldraw model would work just fine.
if you going for lego games look then you would need to edit geometry accordingly, to acomindate additional bones and joints.