- Asura used Rasengan, a jutsu invented by Minato approx. 980 years later.
- Indra used Kage Bunshin no Jutsu, a jutsu invented by Tobirama approx. 900 years later.
- Indra had Sasuke's MS pattern, despite MS being unique. You can't tell me that Sasuke has the pattern because he's a transmigrant either, because Madara was too and his pattern was unique. We've even seen Indra's pattern.
- Hagoromo possessed Mangekyou and used Susano'o... despite the manga nor databook labelling him as a user.
- Asura had Mokuton.
- Asura got given power as opposed to it blossoming through hard work.
- Hagoromo was portrayed as weaker than Asura as an adult.
The list goes on and on...
-The guy who said Minato invented rasengan could be wrong, he doesn't know Ashura.
-Same for Indra's kage bunshin.
-Sasuke has a choko tomoe like Madara, Sasuke was destined to > Madara because of him having Indra's MS.We've seen Indra's pattern, but we don't know how old he was when he got that spiral pattern, that could have happened after he awakened the original MS.
-The manga never said that Hagoromo never had a sharingan.
-The manga never stated that Ashura didn't have Mokuton.
-You misinterpreted that part, it was clearly said that love and cooperation was what made blossom power in his body.
-Hagoromo was portrayed as a guy who doesn't want to use excessive powers anymore.
Please go on.
edit:
Ashura having created rasengan makes perfect sense, and it is canon.
You know what happens when you use bijuu chakra to make a rasengan?Yes, you obtain a special rasengan, a bijuu dama, and Ashura using a bijuu bomb is canon.
That's how the bijuus learned rasengan (bijuu dama), Ashura tried to make a rasengan while in bijuu mode and he made the bijuudama, the beasts then passed down Ashura's heritage.
Ages later when Ashura was completely forgotten by the whole world, Minato studied the bijuu bomb to remake the rasengan.