Can Brazilian jiu-jitsu replace other martial arts?
No, and it was never meant to.
Brazilian jiu-jitsu is a great martial art, and it has many of the answers to the problems that a street fight might throw at you.
But BJJ is not, nor was it ever intended to, be the ultimate martial art.
Brazilian jiu-jitsu black belt Eli Knight explains why in this excellent video:
I think that jiu-jitsu has a lot of the answers, but it’s not the most superior martial art in the a given context. You might need to train for the knife, and the gun, and the other other forms of martial arts, too, to make yourself a more complete martial artist, giving yourself a more complete answer for self-defense.
Professor Eli continued:
It [BJJ] wasn’t pitched as, “Our martial art is the best thing in the world.” It was pitched to us as a great martial art that can supplement your martial art that already exists.
You can watch Professor Eli Knight’s video below: