I don't know why this bothers me so much.
If you're a good blue belt in BJJ training BJJ for "self defence" is dumb.
I train BJJ because I love the art, it's a great workout, and I find the path to mastery to be deeply fulfilling. But if I was really worried about self defence at this point, it would make far more sense for me to learn how to box and (properly) wrestle.
By all means, there are massive self-defence gains you will make from being a fresh white belt up to blue belt. But once you attain a certain level of competence in BJJ, the marginal returns on self defence application are infinitesimal.