You kind of trivialized this by saying that if there is no problem there is no need for a solution. But in real life we are interdependent in non-obvious ways, and need more sophisticated solutions than shooting each other.
The need for sophistication is obvious. Protecting your land is an easy case, but wouldn't you want to protect your future interest too and have a say in what I'm allowed to do on my own land, if that is something that could permanently damage the ecosystem in the long run. Or if I start selling unsafe, addicting products, the libertarian approach would be to let everyone decide for themselves, and subsequently fend for themselves. But isolated people are more suspectible to manipulation, and children too, everyone can be. The libertarian approach would be to leave people behind in the name of self-governance.
The question isn't even should self-governance be our goal, the question is whether it can exist at all. It's kind of an oxymoron, because nobody can protect their rights just by themselves. Building a trust infrastructure is perhaps more important.
