Define "BLM", "protests", and "success" because any combination of different variables produces a different result. Additionally, even then, there is a lot of nuance to being successful when it comes to political movements.
The protests undoubtedly brought more attention to policing and racial issues in general. They obviously didn't solve either problem. Some states passed progressive policing laws, some regressed out of spite or in reacting to the other states.
Then you also have the category of "well, it might have made an impact on this but we'll never know". For instance, does Biden win in 2020 without the Black Lives Matter protests? No idea, and nobody truly does or even can. That would be an enormous impact on many things, some of which may not even have been goals of the protests.