Their grammar is certainly wrong if you'd judge it as standard English, but it has its own logic and the ability to express some things more efficiently than standard English does. You could, and I'm pretty sure people do, consider it a dialect which depending on how history turns out might, over time, develop into a separate language.

For the sake of comparison, consider Afrikaans, the language of most white people in South Africa (the ones that have English as their first language are a minority, though conversation among mixed groups is almost always in English). As you may know I'm Belgian and my native language is Dutch, the same as the original white settlers of the Cape Colony in the 16th, 17th century. They maintained their language there, even after the British conquered the colony, but over the centuries it did evolve. Nowadays, they call the language Afrikaans, and to a Dutch speaker, it reads and sounds kind of like how a 2-year old would speak Dutch - the grammar appears drastically simplified, e.g. no more conjugation of verbs, and they have some hilarious or very cute (to us) words in their vocabulary. But obviously for them it's just their language and there is nothing childish or cute or ungrammatical about it. And although a Dutch speaker may think, Afrikaans is so cute and simplified that I can learn it in five minutes, well, turns out it does take effort to learn like any other language, because they do have a grammar and internal logic of their own that Dutch speakers wouldn't know.

It's certainly important for speakers of AAVE to also know correct standard English. But that doesn't mean that there can't also be a place for AAVE in their personal lives, they can use both depending on the context and the person they're talking to. And there will no doubt be things which they can express in a better or more beautiful way in AAVE than in regular English.