If it was only a matter of 'once-every-few-years' then current emergency capacity will suffice. The problem is that:

A) It happens often enough to be a problem emergency capacity can't handle.

B) Natural gas is not always an option (especially when Russia is the only readily available seller in the area and you DON'T want to be dependent on a potentially hostile neighbor).

C) Existing storage solutions require a massive investment in local solutions, or in the national grid if storage is centralized.

We need to re-think the entire idea about energy always being cheap and available, while somehow preventing those with more money from simply monopolizing supply by outbidding everyone else. You won't solve that with batteries. Many therefore try to maintain the current situation by doing this the old way.

A. We handle dankelflaute's now, and as long as we don't decommission gas peakers, we'll still be able to continue to handle them.

B. Europe has lots of natgas storage. 100 days of storage isn't enough for independence from Russia now, but if we're only using gas for dankelflaute's 5 days of the year, thats ~20 years of storage.

Batteries are extremely cost competitive today for overnight storage, and are marginally cost competitive for weekly storage. That's enough to handle everything except for a dankelflaute. In which case see above.