Hence the qualifier of large scale.
That's what makes the MJ energy ecosystem so good - it works a lot like real power. In real life, you want to run your nukes full out as often as you can, because you can't simply shut them down - you get Xenon precluded startup and lots of nasty exotics.
Same deal with large coal plants - you have to be running pulverizers, get it all warmed up and primed, and it takes a day or two to ramp up from nothing.
Meanwhile, hydro power can be ramped up nearly instantly (and it's clean!), and natural gas turbines can spin up in about 20 minutes easily for power demand response. Wind and solar are entirely different things IRL, so I'm not even going to go there.
There is no one size fits all solution, it's a question of how you run your system. And that's the fun part.