A defense attorney does in fact have duties that aren't in the client's best interest. The court has rules. Each attorney's first duty is to uphold those rules

A defense attorney does in fact have duties that aren't in the client's best interest. The court has rules. Each attorney's first duty is to uphold those rules, and the second duty is to argue for the client to the extent and in the manner those rules allow. This seems quite similar to the process and rules that govern air traffic safety and its incremental improvement over the decades.