There will not ever be accurate data. We still don't have accurate data for the most common infectious viruses. The cruise ship data is the best we will ever get.
This "flattening of the curve" bullshit is an influenza response protocol that depends on the seasonality of the influenza virus and some major assumptions to maybe, possibly work if things go just right. As to preparation time, why would you expect them to effectively prepare now when they have refused to before now?
And yes, if the curve is flattened, there will likely be greater opportunities for the virus to mutate into a more deadly strain.
The evaluation metrics are all specific to the flu as well. It's like evaluating a mule based on race horse evaluation metrics. That mule may be just fine for a mule, but if you think it should be a thoroughbred horse, it will look an ungodly aberration.