Valid, but observe
Galaxy 2's initial trailer.
In there, we see Yoshi properly implemented in 3D, we see new ways of getting round the levels with his tongue lash, we see the fruits that he uses, we see the drill powerup and the applications that it has in gameplay, we see the freezing of a water level and the transition it makes to an ice level, we see the combination of 2D space and 3D space in a way we hadn't seen much before, we see the use of the slowdown switch to navigate an incredibly fast level, we see a level where the ground is constantly changing, deforming and cutting itself away beneath your feet, we see Flipswitch Galaxy and the way that an action you have taken for granted in Mario changes the makeup of the level, you see the shadow Mario concept in action... and this is just for the trailer for the perceived expansion pack sequel!
Comparably, 3D World shows off multiplayer, the cat suit and transparent pipes. I don't deny the wall-climbing stuff with the cat suit has potential for interesting gameplay, but that aside there's absolutely nothing to compete with the lurid ingenuity of that Galaxy trailer, never mind the finished product itself. I accept that they might be hiding the scope, innovation and genuinely new mechanics that 3D World has, but I have severe doubts.