The dictionary definition of an accent is a "distinctive mode of pronunciation of a language, especially one associated with a particular nation, locality, or social class." I think this is underinclusive for how the word accent is used in daily life but, based on that alone, AAVE is an accent. However, AAVE sounds like white people shit in the same vein as latinx. There's no one "black accent" in America, just as there is no single white accent. Accents in black communities vary by region too, NY, ATL, Baltimore, St. Louis are all going to have different accents. But to your point, sometimes subtle differences in accents do just amount to slang and the words chosen for things.