Mako is a metaphor for unrenewable resources. FFVII is largely a cautionary tale, like all the gritty sci-fi that preceded it. Since '97 we have only seen the rate of troubles caused by the 1% and our corporate puppetmasters increase in speed and intensity. Oil, like mako, doesn't last forever. Oil, like mako, like coal, is made of ancient life.
The game makes no attempt to glorify coal. The wind generators in Cosmo Canyon are a visual alternative, but Cosmo Canyon is reclusive and parochial -- no one living in developed areas has considered renewable energy sources. The difference between the two is too abstract to parse, and not worth mentioning. Again, a cautionary tale.