The issue is rather that due to the unpredictable nature of renewables, sometimes the stars align so that the combined output of wind, solar, and hydro end up far beyond what the grid needs.

During those times, in some parts of Europe for example, renewable energy really is practically free. This is a problem for nuclear and fossil plants which lose money during those times. The renewable operators don't make much either but at least they don't have very high input costs.