What Is It About Super Mario 3D World That Doesn't Make It a "True" 3D Mario Game?

[PigPen]

It's a brand new 3D Mario game. Before someone quote me saying no sh!t Sherlock, it's the first 3D Mario with four player co-op that players have the abilities of Super Mario 2 and that's huge. This has never been done with a 3D Mario game ever (not talking Mario Party). A true Super Mario game.