Why nardo didn't learned any more elemental jutsus besides the wind rasengan?
Because he didn't need to
He did multiple element ransengan in his battle against Madara and the last fight with Sasuke.
Didn't he use like a brazillion different rasengans?
>>161590869
Because his role in the manga was to be the one trick pony.
>>161590869
He had natural affinity with wind, so didn't bother with the other elements
>>161590869
It's literally the best jutsu
But i believe that only using his wind affinity to alter the rasengan was a miss opportunity. I mean, he could have done more interesting techniques than just using the rasengan for everything
https://youtube.com/watch?v=lgS8zGnondw
OP BTFO
>>161590869
Cause Kishi a Shit.
He would have had SO much potential with it, Especially with things like sage mode//Kurama.
But that isn't the story that was told. It is the story that SHOULD have been, though...
They said that most Ninjas only had 1 elemental proficiency/affinity. "Genius" ninja would know too (ie Sasuke knowing Fire/Lighting), and more than that was Plot Armor Special cases.
But he did have different Rasengans, normal, oodama, wind, wind shuriken etc.