I find this statement almost funny, nothing could be further from the truth. Capitalism is brutal alright, but honest it absolutely is not, if anything it is the inverse of truth. Imho capitalism is just sales pitch, lies and part truths told to sell narratives, often at gunpoint. The statement itself is yet more of the same. It would be quite at home as something said at gunpoint, it's an opinion of something that suits the agenda of whoever says it, forcefully, and has the power to say believe it, or else.
Energy is real physical truth, it can't be created or destroyed, just pushed around, and if we see flowing energy in presence of stored energy, we see quickly that flowing energy has far greater value than stored energy, because the former is unlimited.
Capitalism is all about limiting everything, including truth, yet real truth is unlimited, like the energy of the sun is unlimited, relative to any store of it, on Earth or otherwise.
Capital is only stored energy.
Engines, always run on flowing energy, not energy stored, though some stores of energy in an engine are useful and required, the engine only generates value when it is running.
Not all engines create pollution btw, some do the opposite.
Right now we have such an engine in humanity which is capable of running, cleaning up all mess of pollution, undoing the history of pollution, but is being stopped from running by capitalism.
This is whilst the economic activity within capitalism still spins in ever decreasing circles, consuming its own output, eating its own tail, at some point it has to fail because it is impossible for it to continue.
Caoitalists are inside that hard limited system with no view of the outside, to indicate to them that the run of capitalism is coming to an end because it has physical limits that can't be gotten around.