False equivalence. The true equivalence would be complaning about him fighting with his legs only, which is not what I'm doing. Luffy doesn't just stretch his body, he's very creative and came up with cool and unique techniques like G2, G4 or Snakeman. But what's unique about kicking fire or lightning ? Million of characters can do similiar stuff. Something like Rokushiki is much more interesting, because not only it has much less often been seen but he can use his own variations of those techniques to make them more unique. And that's just one example.