You could actually use nuclear for stabilizing the grid. The reason no one does so is that you need to run nuclear power plants at reduced power, rendering them even less economical.

If there is no wind or sun, we’re facing a global apocalypse.

No, we're facing nighttime. That happens literally every day.

Growing plants just to use them for energy production is absolutely stupid and incredibly harmful, agreed. But there are types of biomass that are basically waste from food production or forestry. It's not a ton of energy, but it may play a part somewhere.

Batteries, at the colossal capacity required for this purpose, are nowhere even close to existing.

First of all, nuclear is anything but reliable. Germany had to supply huge amounts of electricity to France last year because half of their nuclear plants had to be shut down. They would have had major blackouts without support from their European neighbors.

But my main point is that baseload power does not mix with renewable sources at all. Using batteries and other solutions to store renewable energy during times of little wind or sunlight is actually the goal. But that also eliminates the need for baseload.

Baseload was never really a feature anyway, it was a necessity. Nuclear and certain types of coal power plants were unable to follow demand, they had to be run at close to full load all the time, either for technical or for economic reasons. To compensate for that, other more expensive plants had to be used to cover times of higher demand.