Modern grids favour flexibility over fixed baseload generation (like nuclear) though. When you turn off a nuclear power plant its operating costs basically stay the same, which is horrible when you could cover your whole consumption with basically free solar/wind.

actually nuclear is terrible in a grid increasingly full of nearly-free variable sources (solar&wind). The nukes need to stay at 100% all the time selling their power at a high fixed price to have any remote chance of being economical. Cheap variables push nuke's expensive power off the grid during the day, and increasingly into the evenings with batteries. This is deadly to the economics of nuclear.