France has 80% nuclear. It works there not because French reactors can respond meaningfully to short-term meteorology, but because: 1) France is connected to a continent-sized grid and 2) All of France's neighbours are nowhere near 80% nuclear, so will buy this baseload power.

If Germany, NL, Denmark, Spain, UK et al. had 80% nuclear France's nuclear power would become uneconomic.

It's the grid and unique political considerations, not those plants' responsiveness that makes it work for France.