It's definitely not a magic sword and has been explained countless times how it works. Enma doesn't have power on it's own it just uses the users own Ryuo nothing more
And a piece of metal sucking out it's users Ryuo isn't magical, it makes complete scientific sense.
Hell Ryuo/Haki itself is not magical bullshit either, it's all completely scientific.
A soldier with a modern rifle will have more combat capability than someone using a WWI rifle.
Being able to tap out more haki than you previously could at one time is a magical boost. Deal with it. It reduces combat longetivity in return for greater AP than you could naturally release normally.
If they gave Luffy gloves that allowed him to surge out massive amounts of Ryuo in single attacks then that would be magical boost too.
You got caught in a strawman about the no-downsides aspect, it will kill swordsmen that don't have Zoro level willpower, which none of the scabbards have, that is why they aren't using this boost to their potency. Will you acknowledge your whole argument falls flat without this strawman?