You could be forgiven to think that about northern places, but the dark winters are compensated by the long (or even round the clock) daylight in summer. It's still fewer sunlight hours than markedly sunny places like italy or california but not 50% less.
But of course wind is more stable around the year and produces more in the winter when there's more need for energy. And the sunlight is more direct closer to the equator.
The cloudiness is accounted for in the visualization, otherwise you wouldn't see that much variation on the same latitudes. But yep the sun angle affects things too like I mentioned.
see eg this map where scandinavia is the same color as france or southern uk: https://vividmaps.com/annual-sunshine-hours-of-world/
But of course wind is more stable around the year and produces more in the winter when there's more need for energy. And the sunlight is more direct closer to the equator.