>Those periods of near zero production can last non-trivial amounts of time no realistic battery could provide for

There are many options (electrochemical, gravity etc) for grid-scale energy storage of various durations that are commercially-viable today. 0-8 hours tends to be the most needed duration in the US but there are solutions that can store power for days or weeks without losses. Even in a 100% nuclear or gas-fired world storage is critical. During the Texas blackout both nuclear and gas assets failed due to the cold temperatures.