"A good Mordekaiser doesn't need his shield"

he kinda does

Of course it's true. This actually applies to more than just Morde.

A good CSer doesn't need AD to CS. A good front liner doesn't need CC to peel. A good jungler doesn't need vision to know where to countergank.

Basically stuff like Morde's shield are crutches to assist you in doing something. It's great that they can assist you, but if you require them in order to do anything you are lacking in your capabilities.

Same logic would apply to Yasuo also... and I disagree. I haven't played the rework, but I've never heard such a massive PBE revolt on a champ rework before.