Super Mario 2J existed about 20 years ago. Just because we didn't see it here, doesn't mean it's something new. Whether you liked SM2J or not, it represented probably the best they could do at that time, whatever that happens to be. It's not like saying what if we suddenly forget everything we've learned in the 20 years and pretend we went back in time 20 years, what can we do? Throughout the interview you see the Capcom keep on saying how it was great they get to reinvent the wheel, and an inferior wheel to boot. Today we have tools to assist generating sprites, but to do it old school style means they have to do it by hand instead. Today we have more sophiscated music, but to do it old school means their composer has to relearn how to use some totally obselete tools.
The Capcom guy said about how it's all back to good old gameplay that's shooting, jumping, and moving. Go download a movie of someone beating Yellow Devil in MM1 flawlessly, and that is perfection in moving, jumping, and shooting already. You can't get better than this if you purposely restrict yourself to such a limited moveset. Stuff like the slide, dash, wall jump, double jump, and air dash gives you more complicated moveset for more varied gameplay. You can argue some of these are overkill. Certainly we don't need a boss like Kaiser Sigma in X3 where you need to do 2 vertical air dashes just to dodge his basic pattern. But this doesn't mean go back to the Stone Age of gameplay either. Even just the slide alone adds a lot of dimension to the MM gameplay.
