Then the fine line isn't between confession and evidence, it's between justice and vengeance. We're more "satisfied" when the guilty confess as that alleviates

Then the fine line isn't between confession and evidence, it's between justice and vengeance. We're more "satisfied" when the guilty confess as that alleviates some of the need for vengeance. And we do have a need for it since the desire for revenge is often innate and hard to suppress. But that has (rather shouldn't) have any bearing whatsoever on the truth. If such is true without evidence, it's a hollow truth and has no place in justice, which is punishment for guilt on the basis of truth.