This argument generally falls flat due to how Legendary Weapons are developed in POTCO (and further, in TLOPO). Though do understand where the weapons shortcomings are in comparison to an absolute monster like BSB, it's the way weapons with a red text are treated in the game, and the general mentality behind them.
As
@Eric Sailcutter stated in his post below yours, the weapon is still another Black Shark Blade, and that's understandable. The weapons perform similarly due to the general statistical similarities. Its power is generally low with the exclusion of Powerful on the weapon's hidden stat charts, which can be remedied. That's not a difficult issue.
The weapon itself definitely has a future ahead of it, and though it is in a generally better spot regarding the overall performance improvements are both a subjectively difficult and generally difficult conclusion to come to for a weapon due to where it sits in the game's scale of obtain-ability >/=/< viability.
EDIT: In response to
@Arr, post #7.
"So basically they fixed it and then for some reason decided to replace it even though powerful works properly now? That doesn't make sense but oh well. "
> Post powerful-fixes tweaks absolutely BROKE the weapon in its entirety. Believe me when I say during testing the iterations of Jack Sparrow's Blade that continued to include Powerful post-tweaks were absolutely busted. The weapon was comparable, if not more horrifically unbalanced than Heart of Padres del Fuego during the POTCO days.
Powerful in general is a skill that should be kept on legacy weaponry. An invisible damage buff is fantastic when the weapon isn't doing anywhere near optimal damage under any circumstances, but that just wasn't the case during JSB. The weapon performs at legendary status (albeit walking the fine line) well enough in its current state that makes it much more worthwhile to obtain, and generally less of a joke weapon than it was in its previous state.