Markets are indeed useful, but I think the thing that annoys people about libertarians is their belief that markets are _always_ the best solution, and that market failures can’t happen. When reality disagrees with their theory, reality must be wrong for some reason. You mention the difference between efficiency in the creation of wealth versus efficiency of distribution: food production is a clear example of a system that extremely productive, supplying vast amounts of food, so much food that much of it goes in the bin, and yet many still go hungry. If people are hungry when food is available, it is a money problem, a distribution problem, not a production problem.

Do you think that labor and environmental regulations are needed? Historically, industrial polluters only constrain their output when forced to by the state. How do markets control the contents of packaged food? In the US, packagers are required to list ingredients and certain ingredients are forbidden. When the US FDA said, no carcinogens in foods, food packagers complained. How would individual consumers be able to get producers to change behavior? They can’t. The fundamental problem is that in real life, not all market participants are on equal standing.