Historically, coal and nukes were the base load power sources and hydro and gas for the peaks.
That worked perfectly.
Now, we have a mess!
Nukes load follow if they are designed to.do so. The ABWR which the Japanese can build in 39 months btw load follows natively by pump speed control from 50-100% and control rods down to 25%. Those can ramp at 2% per minute with the control rods and 30% per minute with the pumps. With a full flow steam bypass to the condensers they can ramp down in seconds by instantly dumping the live steam directly to the condensers it is then how much inertia do the turbine rotors have. If anyone tells you nukes cannot load follow and do it as well as or better than gas turbines they are lying to you with a political agenda.
https://www.hitachi.com/rd/news/topics/2024/2403_hiabwr.html