every single one of Ember's analyses are based on historical situations. That is certainly useful, and serves to demonstrate an important point - that wind and solar make economic sense.

There is not a single analysis out there that tackles the twin problems of meeting growing electricity demand with a power source that depends on an uncertain and changing climate.

You say "occasional" dunkelflaute, but we have no idea whether occasional is once a season or once a decade.

This is exactly where nuclear shines, because although it is expensive, it insulates a country against the vagaries of external forces. Whether or not that guarantee is worth the price tag is the question a lot of governments are grappling with and they mostly seem to agree that the value is indeed worth the cost.