In electricity generation, it typically can’t be throttled reasonably in a way that allows quick reaction to changing demand. Most reactors’ power output is regulated by changing the chemistry of the coolant, which can only be done gradually, Using quicker control rods for everyday power adjustment rather than only for shutdown and startup, is avoided to avoid uneven, and therefore inefficient fuel burn. While it could be done, it would make nuclear power even more uneconomical than it already is by forcing more frequent shutdowns for fuel changes.
In electricity generation, it typically can’t be throttled reasonably in a way that allows quick reaction to changing demand. Most reactors’ power output is regulated by changing the chemistry of the coolant, which can only be done gradually, Using quicker control rods for everyday power adjustment rather than only for shutdown and startup, is avoided to avoid uneven, and therefore inefficient fuel burn. While it could be done, it would make nuclear power even more uneconomical than it already is by forcing more frequent shutdowns for fuel changes.
Nuclear load following is routinely done in France. You can see more details here: https://www.nice-future.org/docs/nicefuturelibraries/default-document-library/france.pdf
Like solar, batteries can compensate for the difference between supply and demand.