The concept is great, an original way to make a biopic, a genre that is been abused in the latest years, especially the musical ones.
But apart from the concept, the astonishing performance form Viola Davis, that lives in a perfect armony into Ma Rainey's body, and from some interesting moments, "Ma Rainey's Black Bottom" is clearly born for the stage, is a play in every single aspect and the cinematic production didn't do much to make it different, to make it suitable for the screen, especially the streaming one.
Everything is too theatrical: the screenplay full of dense dialogs that overlap, a static, claustrophobic direction and the exaggerated interpretations that most of the time are too dramatic or too elaborated to feel natural, real (expect Viola Davis' one).
Chadwick Booseman was a great actor but even him seems to constantly search the applause or the looks of an audience that is not there, that can't be there.