The problem is that the existing system is in a stable equilibrium. A lawyer generally can't advise most clients to not take a plea deal because not taking the

The problem is that the existing system is in a stable equilibrium. A lawyer generally can't advise most clients to not take a plea deal because not taking the plea deal will have a worse outcome for that client. It's literally the prisoner's dilemma. You have to have all the lawyers and all the clients act in concert. But if someone defects, they get the plea deal (better than getting stuck in jail and going to trial) and the others get screwed.