While some Democratic politicians have neither supported nor created policies that will help tackle police brutality and racial injustice, this case is not true for all of them.
In the wake of the national protests following the death of Geroge Floyd, House and Senate Democrats brought forth the Justice in Policing Act of 2020. The bill includes a wide range of reforms to police departments including creating a national registry to track police misconduct, prohibiting chokeholds, etc.
Democrats themselves have shown and spoken on the need to aggressively tackle the problem. For example, Democratic House Speaker Nancy Pelosi stated that America "can't settle for anything other than transformative structural change".
National protests have brought a renewed energy to Democrats to bring about real, lasting, and effective change to America in regards to systemic racism, police brutality, and racial injustice.