I think I remember Sakurai talking about how the 3DS version was going to be easier than the Wii U version because it's meant to be played on the train while commute to work and school and such. So hopefully the Wii U version will present a greater challenge when it comes to unlocking fighters or completing challenges. I do agree with you, though, that there isn't any substantial... rewarding feeling. It really does come across as kind of just going through the motions until the game says that you're done.
Edit: Holy shit. These changes to Olimar are not good.
Edit: Holy shit. These changes to Olimar are not good.