My explanation for it is Enma's very nature.
Enma was gifted to Oden, and Oden carried it since he was a kid. Since Enma wasn't used to anyone else, it could only suck whatever it could from kid Oden and was satisfied by it.
As Oden grew stronger, Enma sucked out as much haki from Oden as Oden could supply it. Meaning, at any given timeframe, the amount of haki that it expects from anyone wielding it, would be the haki that the Oden of that timeframe was supplying it.
Ultimately, what Enma got used to, was peak Oden tier armament and conqueror's haki.
To be noted is that Oden didn't even know about advanced conqueror's haki until Roger/WB clash happened, meaning that the Enma of timeframes prior to that also never tasted conqueror's haki........and was still tamed by Oden. Giving credence to my theory, since conqueror's haki is a requirement to tame current Enma, but that clearly wasn't the case in the past.
Enma by it's nature is a greedy sword, hungry for haki.
Enma at the current timeframe could no longer be satisfied by any less haki than what peak Oden could supply it. Simply because it got used to this level of haki.
So the Enma that we are familiar with, attempts to suck out Oden level armament and conqueror's haki. Which was why even someone strong like Scabbards couldn't use it.
Zoro finally truly tamed Enma in chapter 1033.
There he says "So Oden was giving you this much haki easily", awakens advanced conqueror's haki, and tames Enma.
This I take as narrative proof for my theory.
Enma wants prime Oden level haki, it won't be tamed by anyone incapable of supplying it with that much haki.
[automerge]1677736759[/automerge]
I addressed this in a previous post, just pasting it out here