Restorative justice is good, but it's not without flaws. One of the big flaws is what happens if the person who committed the crime does not want to engage in restorative justice.

What if they maintain their innocence, and are actually innocent? Sounds like you need a trial, but what do you do if they don't want to bother with one?
What if they maintain their innocence even though they are found guilty, and actually are?
What if they admit to doing it but say they'd do it again?

What I'm getting at is that you need a backstop to make people engage with your justice system if they don't want to voluntarily.

One other significant issue with restorative justice is that society might want a different outcome than what the victim of a crime might be satisfied with. Think of a case where a person is threatened with a gun. The victim is satisfied with moving on after an apology, but what if the community doesn't want the first guy to have a gun anymore?