By this definition all reserve capacity is wasted money. That is clearly false, as demonstrated by the event in this article _not_ leading to failure and harm.
I'm not talking about reserve capacity at the grid level. I'm talking about excess capacity at the individual generation plant level that exceeds the grids capacity to take in. If you can't output the energy onto the grid the only benefit is for local maintenance and you don't need huge amounts of excess capacity to solve that and that excess doesn't help in the event of a large base producer like a nuclear plant going offline because it can't get onto the grid!