A free market does not allow you to dump your garbage on public property, and no economist has ever argued that.
Libertarians generally argue that externalities should either be illegal or taxed, when there are no other practical solutions. Here's a video of Milton Friedman on the topic: https://www.youtube.com/watch?v=0YGfwSvLkC0
on edit: huh, I didn't know about British economist William Forster Lloyd, mentioned in the article, so I guess at least one economist has argued that it will happen (not though, that it is 'allowed' by)
We complain about Government inefficiencies, and that is certainly an area that can be enhanced, however since the Government's enterprise is the entire Nation-state itself, they are better situated to determine the solution. In order to solve these macro issues, I believe we need a better resourced, accountable, efficient and competent government. At this point that would require a fundamental change at all levels though.
However, no government really cares about global pollution. Ie. greenhouse gasses... Or mercury in the ocean. The benefits of the polluting activity are local while the downsides are global.
For that you really need some global government which is going to take a worldwide view when deciding what is illegal/taxed. Unfortunately there are big downsides to worldwide governance too.
Look at plastic and that recycling government propaganda bullshit.
They sold us to the oil companies and now we literally eat and breath microplastic.
If a polluter is polluting on your share of the shared sky you'll sue them into oblivion.
In what court?
Far from being "free of coercion".
If there was only free market, no government and public property was private and owned by everyone living in a radius - then people would just bring a lawsuit in an independent court to the polluters and either veto (pollution slowly killing you) or get financial compensation (think for things like a noisy airport next to your house).
As it is the polluters just need to bribe the correct government official and it's all kosher.
Citation?