Earlier quoted context omitted.
"as long as the average price is above average cost" And that's the killer. Add enough solar and wind and the average price craters, even if solar and wind cannot handle everything (without help from dispatchable sources and/or storage).
The problem with that argument is that it proves too much. It applies to everything, because solar and wind are the same as nuclear, their incremental generation cost is effectively zero once the capital is paid, so you take whatever the market price is. Which means you have a problem. It's physically possible to build enough solar and wind and storage to even handle extended periods of low sun and low wind. But if y…
What drives all this is that the levelized cost of energy from solar and wind is much less (a factor of 3 or 4) than the levelized cost of energy from new nuclear plants.
Nuclear, or at least many existing nuclear plants, has an additional disadvantage: it cannot cut output rapidly. If power from renewables suddenly floods the market, prices can go negative. Renewables can just stop selling in that situation, but nuclear is forced to continued to run and eat the negative revenue. The low power density of the renewables sources, usually depicted as a negative, is the source of this advantage: sunlight absorbed in PV modules can just be allowed to dissipate as heat there with no negative effects.
(In fairness, I should also mention that there are subsidies in the US that encourage renewables to keep generating even at negative prices. These subsidies will have to go at some point, and perhaps that point is now.)
What will be the final death knell for nuclear will be when short term storage gets cheap enough that the times when that's discharging will also be economic death zones for nuclear plants. I expect few of the existing operating nuclear power plants to survive after that.