The metaphor is good in the sense that when you depend on sun, wind or even hydro power you lack much more control than when you have a fueled power source. Barring mechanical failures (which can always be minimized with proper maintenance) you have much more control (at least in a short term) when you depend on fuels.
That is incorrect. Modern weather prediction is now so good, the wind can be predicted a week in advance better than it could be a day in advance in the 1990s. For that reason, you can now know ahead of time how much power a wind farm will produce, with considerable accuracy. You can schedule maintenance for days when there will not be much wind. Alternatively, when you know there will a lot of wind, you can schedule maintenance on a fossil fuel or a nuclear plant, knowing the wind farm will substitute for the lost power.
Furthermore, wind farms produce power in blocks of ~1 MW each (one tower). When you do maintenance, you take one tower out of service at a time. With a coal gas fired plant, you have to take hundreds of megawatts off line for several days. To refuel a nuclear plant, you have to take a gigawatt off line. Not only that, but nuclear plants sometimes go down with an emergency SCRAM event without notice. That is not often a dire or life-threatening event. It is usually caused by a plumbing problem, such as a storm at sea that causes kelp to clog up the inlet water cooling pipe. But it brings down the whole nuclear plant. Bang, 1 gigawatt gone. That never happens with a wind farm. It goes off a little at a time, in ways you can predict a week in advance. From that point of view, it is actually more reliable and predictable than fossil fuel or a nuke.