You missed my point completely. It's not about the "whims of the economy", it's about demographic change. If there are not enough people to pay into a public pension scheme, then there are also not enough people to generate the profits a private pension scheme needs.
Only if the economy goes down and inflation goes up. At the moment, inflation is low and the economy is growing.
My problem is not so much that I'm exposed to the whims of the economy, because that's unavoidable. My problem is when I need to pay extra so others don't have to feel the whims of the economy while I get to feel it double.