The BLM protests did work, they exposed that the US is a violent police state where voting doesn’t actually do anything to change whether we live in a violent police state because both the Republicans and centrist Democrats will collaborate as much as needed to betray their voters in order to sustain the system of policing and prisons.
The fact that in the wake of George Floyd a lot of cities and municipalities actually went more draconian with their policing laws in backlash is only an indicator of a failure of the BLM protests if you don’t look closer, step closer and you see the truth is far scarier, the BLM protests did massively change the psyche of America, it’s just that actually has no effect upon policy making because democracy is so broken in the US to the extreme point where many city governments chose to actively do their opposite of the will of the people as a show of force and a chilling warning to leftists.