Shaving some of the *predictable* daily peaks is nice. It brings you closer to the base load demand and saves a bit at the margin.
Responding to a sudden and *unpredictable* loss of a good fraction of your power generation capacity is no longer about shaving. I think the right term would be "amputation". The cost at which a large fraction of consumers would plan and respond by reducing their power demand is about the same as their losses from a blackout. This is no longer about optimization of resource use - it's about spreading the inevitable damage to those for whom it is slightly less painful (or those who simply have no choice because they cannot pay).
This is way past the point of diminishing returns on overall benefit to society - unless you ascribe some value approaching infinity to your religious devotion to "renewable" energy and make everyone share this valuation by force.