You need load following to keep up with shifting demand, that’s absolutely required and the only thing actually required. Intermittent and base load on the other hand is simply cheaper than load following which lowers production costs vs a 100% load following grid.
Intermittent sources can actually provide a much higher percentage of annual power than base load sources at a lower cost per kWh.
Load following is the 1st category historically, currently filled by hydro, gas turbines, and batteries.
Base load was the 2nd category which was less flexible but historically cheaper coal and nuclear. The only advantage it has over load following is price.
We now how a new 3rd category intermittent generation which is also cheaper than load following but just like base load it can’t follow the demand curve.
Therefore replacing all base load generation with cheaper intermittent generation is absolutely fine as lone as load following can pick up the slack there is zero downsides.
PS: Nuclear doesn’t actually lower peoples electricity costs. The difference is people in France are paying a percentage of their electric bill in taxes rather than as a separate bill. That’s great for poor people, but less so for the economy.
That’s critical because nuclear really doesn’t fit very will in a renewable heavy grid. Given the choice of nuclear + hydro + batteries or solar + wind + hydro + batteries the solar + wind grid is vastly cheaper.
Having said that, some nuclear is likely to be cost competitive without subsides in 2060+ somewhere.
I'm very much not anti-nuclear but I do wonder if we've possibly missed its window. To me, a plausible two-step solution to decarbonization would be (or could have been): 1a. Replace all the fossil fuel base load generation with nuclear/hydro, 1b. Replace all the variable load natural gas plants with storage, 2. Now that storage is mature and scalable, replace all the nuclear with solar/wind.
The reason this makes more sense in my head is that renewables are actually more dependent on natural gas than nuclear would be, in the current world of limited storage. I agree with you that once storage is built out, the role of nuclear is a lot less clear. But I think you'd have to say that it's still an open question whether we can really make storage scale as much as it needs to if it's going to support a fully renewable grid. It has only recently started to seem like the answer to that may be promising.