Pure head canon you have no idea what rank Shusui was before Ryuma turned it into a black blade and what matters is as of this moment it's still same rank and quality as Enma alongside the rest of the other 21 excellent grade swords.
Hitetsu literally says that forging Enma into a Black Blade will raise it's rank. Ryuma forged Shisui into a Black Blade, meaning he raised its rank from what it previously was. Damn that Oda with his headcannon of his own manga.
Zoro has always shown absolutely ridiculous amounts of AP starting back in Dressrosa where he was cutting up giant Pica like butter Enma has very little to do with that. Zoro trained himself to be able be wield it so if he grew stronger that's due to the training he did not the sword itself Enma drains users haki
Back on Dressrosa, Zoro opted not to send flying slashes towards Pica because he said he was too far away, and they wouldn't be able to knock him out. On the rooftop, with Enma in hand, he sent a a flying slash clean across the massive skull, which cut off the massive horn of Onigashima, with no signs of the attack slowing down. He did that with Enma alone.
Sword can't be dangerous on it's own Zoro used insane amount of his haki into that clash the danger is from it's wielder you guys are running away with this because Oda always hypes any new sword Zoro gets and twisting it
It's literally stated in the manga. "Look out Kaido,
THAT'S NO ORDINARY SWORD."
Kaido sensed Oden's aura around Enma which makes sense that was one of the sword that scarred him and used by Oden his whole life
The ability to damage Kaido is entirely about the swordsman capabilities hence why there was not single word about Enma when Zoro used Ashura to scar Kaido. A feat only Oden managed so if it was all about Enma this was the time to, it makes no sense why Kaido would not mention how it wounded him instead he was surprised and shocked by Zoro
No, he didn't sense Odens aura AROUND Enma, he said, "How does that Katana, bear the presence of Oden,
WITHIN IT.
And I don't care what Kaido did or didn't say when Zoro scarred Kaido. You guys just need to quit acting like all this shit Oda has emphasized about Enma doesn't mean anything. Trying to pretend like the Sword was some kind of nerf is one of the worst excuses you guys have come up with.