You speak as if we're in a functional system where people are safe, getting here was smooth sailing, and I'm proposing a preposterous idea. Our system currently does not work and billions have died to get to this fucked up place. Why would you think a different system will fail because it is not like just the current failing system?

If I see a guy shoplifting and just shoot him, who is in a position to tell me that I was wrong

The community, a functional anarchist community wouldn't tolerate this, it would become a crime in itself. A functional anarchist community would defend itself and have members ready to do so. If somebody shot another person for something like shoplifting (which wouldn't be a thing in anarchism duh) that would be murder and that person would now be at risk of termination as a mortal threat to the community. People don't usually desire to escalate things though, so contrived examples like this are silly.

You can’t have some lackadaisical ad hoc minute men arrangement, there are too many humans and too many competing interests for that to work in the modern world.

I'm not one of those that thinks anarchism is a drop-in replacement for capitalism or that anarchism can come from violent revolution. If anything close to anarchism could ever happen it would take at least a couple generations (of cultural change) and co-occur with degrowth. We know that our current system is unsustainable, so we're either going to end up with something like anarcho-communism + degrowth or we won't exist anymore. There is no way a hierarchical system that exploits that planet to support billions will be able to exist beyond the next decades, can't happen. Even socialism just makes things more equal while we destroy the planet.

I’ve never once met an anarchist who can coherently explain how, in a practical sense, you ensure justice and order at a large scale without a state, legal framework

The scale and ways of life now are the result of an exploitative economic system. Without that it's not our nature to form into efficiently exploitable structures. We'd form into manageable communities as humans have done for hundreds of thousands of years prior to the appearance of the state.

Who makes sure my lights stay on and that my landlord didn’t use asbestos and lead pipes when...

You and your community work to keep the lights on and other needs met. For asbestos and lead pipes, the motivations to do these things come from an exploitative economic system. In anarchism, if someone sells you poison, you can defend yourself. There won't be many people selling lead pipes when their life is on the line rather than a fine or job loss.

You can’t just have mob justice or random individuals deciding based on their own arbitrary, subjective opinion how to carry out justice at any given

So instead we should have the opinion of the rich powerful racist people enforced by people with a license to kill and who use in inordinately more often on vulnerable populations who cannot legally protect themselves?

Does that person’s wife or brother now get to shoot me?

Yes, and the community might say, "well, he deserved it, have a taco". Our current system basically allows most men to rape women and the woman has no recourse because the state protects the rapist. This is not a working system.