It’s not post modern to recognize normal occurrences that can neither be stopped nor steered. It’s refusing to spit in the wind. Languages evolve, that matter IS settled. Good, bad, evolving happens.
There is no “evolution”. There is simply change, and that change can be good or bad. It can be change toward standard english or change toward Ebonics. We, individually an dcollectively, get to choose, and if we choose wrongly the culture and the life of the mind is degraded.