Baseload was a cost optimization. Back in the day it was cheaper to build coal & nuclear plants that took days to power on. Somebody figured out that if a grid was built of a mix of those cheaper plants and more expensive plants that could start up quicker, it would lower costs. The typical grid was baseload coal and gas peakers. But ~20 years ago gas peakers became cheaper than baseload coal and any need or desire for baseload generation went away.
China is building a lot of coal plants to complement their solar buildout. Notably these are not base load plants. Their new coal plants do not run 24/7, they only run at night.
Similarly, many new nuclear plant designs are not base load designs; they are designs that can be safely and quickly turned on and off.
P.S. the correct term for generation is "non-dispatchable", not "baseload"
