Pumped storage is great, but it is only a partial answer. You describe the "supply shaping" aspect of grid management, where we assume the demand for power is outside of our control, and we adjust our supply to meet whatever is being demanded. The problem is that pumped storage is not scalable. There are only so many places you can build reservoirs.

We need to focus on "demand shaping". Instead of (or rather, in addition to) putting power into storage so we can take it back out at a different time of the day, we need to shift our consumption of power so it is used when it can be produced.

Supply shaping is the flattening and shifting of the supply peak to match the demand peak. It is far more efficient and scalable to flatten and shift the demand peak to match supply.

We need large appliances like home and commercial water heaters and deep freezers to be directly aware of grid conditions and temporarily adjust their setpoints a few degrees.

Steel production, aluminum smelting, and other heavy industries are commonly done overnight during the demand trough, where they increase the base load and reduce reliance on peaker plants. They need to be shifted to daytime operation during the supply peak.

We need massive energy sinks such as desalination plants, hydrogen electrolysis plants, and Fischer-Tropsch synfuel production plants collocated with and powered by solar, wind, wave, and tidal energy facilities. They need to suck up any cheap, free, or "negative rate" power they can get, but shut down production and back feed the grid with their own generation when prices rise during the day.