You just haven't looked enough, it's far from the worst Nintendo has produced in the past years. Play-wise, it suffers a little from the way the controls on the 3DS are made compared to the way the GC controller works, and it's no surprise that Nintendo is actually bringing a GC->WiiU adapter this xmas season. Otherwise it feels and plays like a SSB game, with a wide enough roster (remember, SSB on the N64 had a roster of only 12, SSBM had 26, SSBB had 39, and this one has 49-51), a variety of play modes, challenges, and a lot to collect and personalize for the obsessive collectors and overachievers out there.
If you want actual bad Nintendo games, try Steel Diver: Sub Wars (it's a free game on the 3DS eshop), Pokemon Battle Trozei, Yoshi's New Island, Mario & Sonic at the Sochi 2014 Olympic Winter Games or Game & Wario.