The article says Diablo Canyon generates 2,250 megawatts.
https://en.wikipedia.org/wiki/Solar_power_in_California says "The Solar Energy Industries Association predicts that California will increase its solar capacity by over 27,000 MW over the next five years".
According to the chart titled "California Solar PV Capacity by Year", they added two Diablo Canyons worth (4,779 MW) of PV capacity last year alone.
That is, Diablo Canyon actually puts out 2,070MW of power from it's nameplate 2,250MW. While 4,779MW of PV in California will generate 1,385MW of power.
So, they really only added half of a Diablo Canyons worth of capacity last year. (Still an impressive amount of power, but not as much as it seems).
Electricity grids do not have the luxury of being able to shut down, they must meet the demand every day of the year, every minute of the year
Technologies with an higher capacity factor are inherently more valuable than the ones who don't and technologies with an unpredictable capacity factor are worth even less than those two.
Neither nuclear nor coal are very dispatchable, as they can not respond to changes in demand in cost effective ways. Gas turbines can easily, as can batteries. While the sun is shining, solar can be dispatchable, because it's easy to shut off on demand or turn on demand. But for 60%-75% of the day, solar is not dispatchable.
In the modern grid, dispatchability is a far more useful attribute than capacity factor. Capacity factor is just an incidental.
What matters then is the reliability and this is why the capacity factor and especially its variation are critical. See what happened in the EU when the russian gas turned off.
Batteries are a low scale solution at best at the moment anyways and aren't working at the scale of a grid.