Why is a thread complaining about how short SM3DL is disguised as a thread about how Nintendo complained about its sales? I can't find a single news post that says Nintendo are disappointed with the sales. Considering that it is the first 3DS game to sell 5m copies, I imagine they can only be happy with the success.
Yes, the levels are short and the game is easy, but it's still a thoroughly enjoyable game. If you want to stretch it out a bit, set yourself some challenges like getting the fastest possible time in all the levels (or repeatedly hitting Toad 3 times with the same boomerang ). There are already many threads you can discuss this in, one of which was created last week and is currently further down this forum's first page of threads.
Yes, the levels are short and the game is easy, but it's still a thoroughly enjoyable game. If you want to stretch it out a bit, set yourself some challenges like getting the fastest possible time in all the levels (or repeatedly hitting Toad 3 times with the same boomerang ). There are already many threads you can discuss this in, one of which was created last week and is currently further down this forum's first page of threads.