I think you have that backwards: in the US, we lack the ability to scale down coal and nuclear plants. Solar and Wind are generally the first to get pulled offline when generated capacity exceeds demand and storage.
TIL this is called "curtailment" and it's an argument that utilities have used to justify not spending on renewables that are saving the environment from global warming (which is going to require more electricity for air conditioning).
Solar energy production peaks around noon. Demand for electricity peaks in the evening. We need storage (batteries with supercapacitors out front) in order to store the difference between peak generation and peak use. Because they're unable to store this extra energy, they temporarily shut down solar and wind and leave the polluting plants online.
Consumers aren't exposed to daily price fluctuations: they get a flat rate that makes it easy to check their bill; so there's no price incentive to e.g. charge an EV at midday when energy is cheapest.
The 'Duck curve' shows this relation between peak supply and demand in electricity markets:
Developing energy storage capabilities (through infrastructure and open access basic research that can be capitalized by all) is likely the best solution. According to a fairly recent report, we could go 100% renewable with the energy storage tech that exists today.
But there's no money for it. There's money for subsidizing oil production (regardless of harms (!)), but not so much for wind and solar. There's money for responding to natural disasters caused by global warming, but not so much for non-carbon-based energy sources that don't cause global warming. A film called "The Burden: Fossil Fuel, the Military, and National Security" quotes the actual unsubsidized price of a gallon of gasoline.
Wouldn't it be great if there was some kind of computer workload that could be run whenever energy is cheapest ( 'energy spot instances') so that we can accelerate our migration to renewable energy sources that are saving the environment for future generations? If there were people who had strong incentives to create demand for power-efficient chips and inexpensive clean energy.
Where would be if we had continued with Jimmy Carter's solar panels on the roof of the White House (instead of constant war and meddling with competing oil production regions of the world)?
It's good to see wind and solar growing this fast this year. A chart with cost per kWhr or MWhr would be enlightening.