Any system is only as good as those that practice it and administer it. You can argue that we're getting more civilized every day, but without a system of law and order where people are held accountable for their actions, society breaks down.

Think about what would happen if someone was murdered in your hypothetical utopia - should the victim's family have compassion for the alleged assailant? What if an individual was unable to defend themselves? How would the family react? While we'd all like to be optimistic and think they would embrace compassion, how often would that really happen in practice? How can you even hypothesize and pretend to put yourself in that scenario when there are a million different elements that contribute to the taking and outcome of a particular action? As we can see from what's going on in America right now with regard to police bias and brutality, when citizens take matters into their own hands it escalates tensions and the effect further polarizes people.

Furthermore, just because we are rapidly developing technology and live in an interconnected world doesn't necessarily mean we're more civilized. While it's beneficial to be exposed to different cultures and people across the world, it also means that there are more ways to reach extreme audiences and spread misinformation.

I agree with your assertion that a focus on healing as opposed to punishment is needed and would yield better results, but it's naive and impractical to think a system without accountability would be sustainable or anything less than disastrous. Without incentive to not commit crimes and immoral acts, the rate at which such acts were committed would increase. Also an individual or group's definition of force vs. violence is subjective and therefore dependent on who is interpreting the relevant actions, which also complicates your murder and self defense position. What if someone believes self defense means protecting their honor and they retaliate because someone insults them or perhaps assaults them and then someone ends up dead? Laws would help in that situation, wouldn't they?

A focus on learning to rewire one's brain and recognize thought patters that are potentially harmful is a better proposition. Losing accountability for criminal actions would propagate bad behavior. The criminal justice system is deeply flawed and works against many people. Those with the means and deep resources to game the system unfortunately do on some occasions. But that's exactly why it's important to learn the system and educate yourself. It's far from perfect, but it beats a society devoid of law and order. If more people looked inward and asked how they could be better as opposed to outward seeking to find third parties to blame for injustices or misfortunes we would all be much better off.