Storage in the form of batteries, pumped storage, hydrogen, or ammonia works. It is needed more for renewables than for nuclear, but nuclear is hard to throttle to a fine granularity like fossil fuel plants.
Anyway, I should have said power generating capacity is mostly fungible. You can mostly replace any capacity with a different kind, within some limits, the same way money isn't perfectly fungible if you need currency conversion, have FDI limits, repatriation limits, etc.
