Finding a rare cursed blade is something you should credit yourself with, as often it's the case that rare Cursed Blades are harder to find than regular Famed weapons.
Of course, it comes with a pretty good reward. Even the "worst" of the cursed blades are still very good compared to most other weapons, so finding one will more than likely pay off for you. This is also the case why pulling out a Legendary Cursed Blade in front of somebody is such a shock for most people.
But, keep trying! It's all about luck and patience, so if you grab a few friends and head off for cursed waters you'll find one in no time
Best of luck! Happy pirating!