https://www.feynmanlectures.caltech.edu/II_09.html
https://archive.md/PsDm5
Electricity in the Atmosphere
Although the electric current-density in the air is only a few micromicroamperes per square meter, there are very many square meters on the earth’s surface. The total electric current reaching the earth’s surface at any time is very nearly constant at 1800 amperes. This current, of course, is “positive”—it carries plus charges to the earth. So we have a voltage supply of 400,000 volts with a current of 1800 amperes—a power of 700 megawatts!
700MW is a power of a single nuclear reactor or of a medium size hydropower plant.
So it is nothing in comparison to humanity power production and demand. And this tiny amount is not for a few average towns around power plant, but for the whole Earth.
Also, extraction of all that tiny power, not only extremely complex and hardly will even produce enough power to sustain operation of such energy extraction facilities, but also could cause unpredictable changes in ionosphere with completely unpredictable results for whole Earth life and everything.