Comment by jfengel

Natural gas and coal are better at throttling up and down than nuclear plants are.

So if they need to run 10% of the time, then you've still reduced your carbon output by 90%. The goal is 100%, but the remaining fossil fuel plants are not the biggest issue.

A nuclear plant would also be carbon-free, but Germany had other reasons not to want it. So it was a reasonable decision to keep the fossil fuel plants around, and shut more and more of them down over time.