In the English language, power generation is usually separated in two parts, "base load" and "peak load". Of this, base load is a planned supply that follows an expected demand curve, while peak load responds to actual fluctuations of both demand and base load.

However, German comes closer to actual practice by dividing what English calls "baseload" in two: "Grundlast" is a part nearly constant throughout the day, while Mittellast involves the planned variable capacity, which is increased/decreased in say 15-minute blocks.

Now, one thing Mittellast does is balancing the known (and expected/predicted) daily oscillation of demand. But the other is to balance known (expected/predicted) changes in Grundlast, e.g. say the stoppage of a coal power station for maintenance or a nuclear plant for refuelling or post-accident repairs.

When you speak about base load, you seem to consider the Grundlast part only. However, renewables, especially with increasing grid penetration and geographical extent, can be predicted, predicted with sufficient precision to be considered in the Mittellast planning -- the same way the temporary decommissioning of a large coal or nuclear power plant can be. (In fact, for Mittellast operators, they allow for a more efficient operation than having to adapt to 1000 MW suddenly off the grid.)

All of this is not rocket science. High grid penetration wind power is actual reality in Denmark or North Germany

Temporary storage can enable even higher grid penetration. But, so can the up-scaling of grids -- and the combination of different intermittent renewables (solar and wind have a natural compensation in their intermittence, for example). However, such high levels of grid penetration on an EU-wide basis is still years if not decades in the future.

_{*Lunatic*, n.
One whose delusions are out of fashion.}