Earlier quoted context omitted.
As you wrote, redress in the courts is expensive and unlikely to succeed against the government. The USSC made-up doctrine of government immunity should be removed. BLM got side-tracked into ineffectiveness by avoiding this underlying problem.
It's simply because the courts are not in the habit of doing their jobs anymore. They are expected to hold the LEO accountable to the law just as much as the citizen, but the de facto system aligns the executive and judicial completely, such that neither is willing to take action against the other. If the courts were faster, more flexible, they would have more experience holding the executive accountable, and issues…
Government prosecutes criminal law. There are various reasons, including politics or career progression, that government prosecutors overlook some crimes. Individuals don't successfully charge others with criminal violations.
Individuals prosecute civil law. If civil law penalties continue to be unavailable because 'government immunity', then bad actors in government will not be restrained through the courts.
I'm uncertain what court legislation you would propose, other than removal of USSC doctrine of government immunity.