Obviously Madara had it but do newer generations have knowledge about it? Orochimaru seemed surprised in the fight vs Itachi if i'm right.
Even the Uchiha Tablet didn't mention it. At least not to those only with the 3T.Only ninja with high intel knows about Susanoo because it was a rare technique even among the Uchiha.
Bad writing by Kishimoto.i doubt it im sure your smart people know about it like how kakashi knew it but people in naruto seem stupid to me (like how an anbu didnt know who the 1st and 2nd hokage were) un less its just bad writing by kishi