Basically, you end up having to overbuild to crazy levels, or build insane amounts of battery storage, which only gets used a few days a year.
The second point is that the distribution has a long tail, especially when we consider the possibility of multiple independent incidents overlapping in time, to the point where it becomes infeasible to suppose that we could be prepared to continue operating as if nothing had happened in all conceivable scenarios, regardless of how accurately we could predict their likelihood.
We have coal fired plants in Australia with <90% uptime (often unscheduled), but somehow they're considered baseload rather than intermittent.
Things in the US are a bit more of a mixed bag, for better or worse, but there have been studies done that suggest that you can get very high renewables levels cost effectively, but not to 100% without new technology (eg “clean firm” power like geothermal, new nuclear being something other than a clusterfumble, long-term storage like iron-air batteries, etc etc etc).
There are interesting engineering problems for sources that are intended to operate very infrequently and at very low capacity factor, as might be needed for covering Dunkleflauten. E-fuels burned with liquid oxygen (and water to reduce temperature) in rocket-like combustors might be better than conventional gas turbines for that.
Also, if solar ends up much cheaper than wind there's going to be need for seasonal energy storage, which could be considerably more than 2% at high latitude. Batteries are unsuitable for this.