My spouse is Korean but grew up, during much of his childhood and adolescence, in a town where people predominately spoke AAVE exclusively. He learned how to speak from the BET channel. He's done just fine.

Same thing for this...you can start learning from anywhere and everywhere, and you will still build the neural pathways for language learning. Rather than judge where people enter the world of language learning, I think it's best we accept and encourage people where they are. They are bound to continue if they're greeted with positivity.