Yes people do tend to underrate him alot, People completely overlook Enma also, he is quite and OP summon.
Going from what owarij said awhile back, enma might have cloud release and controll of Two elements (wind and water i think), I think he was going off the Jap myth behind Enma, Since kishi does base stuff off old Jap myths and legends
(I could be totally wrong about this, This was along time ago he said this and i cannot remember what he said exactly.
People claim that he is all hype, Yet say nothing of hashirama being almost all hype.
People say the Edo kages wern't at full strength, Yet say nothing of hiruzen not being at full strength.
Also i found this old quote from him, Again this isn't proof, Just an assumption base off the myth behind enma