I would say the problem is more so that renewable energy sources just aren't as reliable as fossil fuels. The sun doesn't always shine, and the wind does not always blow.
Plus these systems are designed knowing that solar and wind power are inconsistent. It isn't a shock to anyone that Central Europe gets less sunlight in the winter.
[1] - https://www.swissinfo.ch/eng/sci-tech/renewables-share-of-el...
The blog just seems to be the ramblings of a covid/climate conspiracy type. I'd take it with a pinch of salt.