More bubble puncturing time! The second law has been extended to systems far from equilibrium where boundary conditions are sufficiently known. It also applies to all work processes and energy conversions where entropic losses end up as non-recoverable heat. In the end the world is a system essentially closed to material flows and in long-term steady-state with respect to energy flow (excepting radio-active decay heating which is diminishing over time and tidal pulses which are probably negligible for our current purposes) as long as the sun is in stable burn. Our burning fossil fuels is just releasing some of that energy that took up residence in chemical bonds temporarily.

What thermodynamics tells us is that there is no free lunch. That energy is on a one-way trip from source(s) to sink(s). It tells us a lot about the energy infrastructure if we know how to interpret and measure.

As far as Mencken goes, he was right. There certainly can be any number of clear, simple, and wrong solutions. So what? There can also be a simple, though apparently not so clear, answer that is right.

Question Everything

"The Second Law Of Thermodynamics can only be applied to isolated systems and the world's energy producing infrastructure doesn't fit that criteria."

For all intents and purposes it is.

You, like so many people, fail to realise that you cannot isolate one aspect of infrastructure, and ignore everything else that we rely on to run our civilisation.

Energetically, yes, the earth is open to huge amounts of energy from the sun. What is limited is our ability to utilise that energy. Our energy infrastructure allows us to use energy stored in fossil fuels (solar energy that biological organisms locked up in chemical bonds), solar energy, nuclear energy and so on, to do work. We use technology to enhance the range of things we can do with that energy, but ultimately all of this relies on us, and we and our infrastructure require the following (and much more besides):

Fresh water
Clear air
Healthy soil
Diversity of organisms (lack of diversity = prone to disease/environmental extremes/etc, e.g. in crops)
Mineral resources
Scalability (for technologies) - i.e. do not rely on other limited resources
Confidence in systems of exchange (financial systems)
Co-operation

If our energy infrastructure is limited by things other than simple inputs, then it is part of an isolated system.

Another failure to appreciate the complexity issue.