I think the core problem is the incentives, like someone said. Agreed. It's even in the design of the system, the DA is supposed to try to convict the suspect

I think the core problem is the incentives, like someone said. Agreed. It's even in the design of the system, the DA is supposed to try to convict the suspect. In and of itself that's not a perverse incentive. The system is adversarial: the DA is supposed to try to convict, and the defense is supposed to try to acquit. Plus the defense has a huge advantage, because the burden of proof rests with the prosecution; the defense only has to establish reasonable doubt about the suspect's guilt. You could argue with it, but it's not an obviously terrible design. The problems are with the implementation, chiefly: (a) the prosecution almost always has vastly better resources than the defense; and (b) judges and juries totally ignore the burden-of-proof rule.