It's not profound to say that sustained (infinite) growth is unsustainable, but it is of interest when it's within a conceivable timeframe.
It's not worth reading however, because the author whimsically extrapolates energy usage starting from 230 years before the invention of the lightbulb to get their exponential growth argument which doesn't hold at all for modern data.
https://data.worldbank.org/indicator/EG.USE.ELEC.KH.PC?end=2...
"But let’s not overlook the key point: continued growth in energy use becomes physically impossible within conceivable timeframes." (conceivable timeframes ~ few 100 years)
As far as I understood, the argument is not "we are doomed" but that there is a natural limit to the growth of energy consumption in the not too distant future using some naive assumptions. In any case, it is implying that 2.9% growth per year is a lot! if it is extrapolated by just a few 100 years. Do I misunderstand something? Why is this controversial?
But I did not yet read all the linked later posts.