riots reasoning behind nerfs to off meta builds

i believe riots reason for nerfing a champion's off meta build (like the nerfs to AD poppy), or rying to force someone into a specific role (skarner, morde, kalista), is because their goal is to have "a unique identity for every champion", and they dont have identities left for new champions. so by forciing a champion into a specific role and giving them a specific generally consistant build path, they are given more room to operate with new champions to stay with this idea of a unique champion. im not saying i agree with this viewpoint or even that they accomplished this goal (ahem xin r camille r), but i do believe this is what they are trying to do.