Isn't the fact that they were not implemented part of the definition of their failure? Since it's supposed to be the backbone of the solution that allows the neoliberal model to continue without significant changes, the fact that it was not adopted is a clear indictment.
The fundamental appeal of these carbon schemes is that they can permit a theoretical decrease in greenhouse gases while keeping the current economic model alive and well. But despite being greatly amenable to the way things currently are, with few extra efforts or changes needed in comparison to other types of plans for the climate, they were not widely adopted at all.
The system these schemes were designed to save was unable to pick even the lowest-hanging fruit that could have potentially saved it.
So yes, it might work with unlimited clean energy, but if we have that we are already in a different arena altogether with entirely new problems and solutions and where carbon credits are unnecessary anyway.
The fact that the cost-structure doesn't work now is the indictment. Cost structures is how we got into all this mess to begin with. Saying carbon credits work is like saying a healthy lifestyle can prevent obesity. It's of course true on its own, but also fairly useless since the problem is that people are very resistant to adopting such a lifestyle.
The subthread was whether the carbon schemes are effective. They are either ineffective because they do not fix the incentive problem, or effective in a context where they are no longer needed
