Friedman and Hayek wrote their work before we had a thorough understanding of how complex systems are optimized. Thanks to more powerful computers, we now know that search guided by purely local improvements gets stuck in local minimum (in Economics, those are the Pareto points). Those local minima can be incredibly far away from a true global optimum, but can't be improved by "consensual and mutually beneficial transactions".
Sometimes you do need to take actions that temporarily inconvenience one actor to achieve a point that will benefit all them in the long term; see the prisoner's dilemma for a simple example. The GP post mentioned 40-hours work weeks; those weren't brought by laissez-faire economics nor individual negotiation either, 60 or 80 hours a week were the norm before socialism.
Capitalism tends to create immense concentrations of power without checks and balances on the hands of tycoons, of the kind that should make any true libertarian be very afraid of those holding it. The system that really works best is one where wealth is created for a few years through capitalism, and then that wealth is redistributed by government's welfare politics to the wider population. This is what has been going on in Western countries in the last century, bringing us stability and avoiding the frequent revolutions that plagued Europe and the Americas in all its previous history.
It would require some constitutional amendment for both sides to trust each other enough.
I'm very tempted to throw in with the former, except that I worry about the follow-on effects of basic income. Would a basic income just be a windfall for landlords, as they all increased rents by some large percentage of the average basic income? Or would the formerly-urban formerly-poor head for the hills, now that they could budget over the long term without relying on urban amenities? This would be a windfall for a different set of landlords and real estate investors, but it would drastically change the nature of 80% of the communities in the nation. That's not even to consider the wealth effects on markets more elastic than housing. It would be a grand experiment, but somebody would start crying.
Tech hiring collusion, 2008 financial crisis, environment degradation and global warming, slavery-like conditions at suppliers of multinational corporations, medical bankruptcies in US and lack of guaranteed holidays, ghettos, plundering of natural resources, monopolies everywhere (as prescribed by Thiel btw).
Such a wonderful, mutually beneficial, ethical system with so many positive externalities! /s
You may claim that capitalism is the "best" system at this point, but to state that's wonderful is indeed indistinguishable from parody.