I don't see how people like you miss the entire concept of "base load".

I live in a region with vast amounts of renewable energy resources. It's always windy and the sun shines almost every day. I have solar panels on my house that cover most of my DHW and a large fraction of my summer cooling load, and keep most of my appliances running.

But right now, the sun is down and the wind is flat. And I still need power. My battery storage would be depleted by morning, damaging it through overdischarge if I don't buy power from the grid instead.

And it's a lovely summer evening with no heating or cooling demand! What about midwinter, -35C and dark and snowy? Where is my power coming from on that day, after a month of days just like it?

Nuclear.