What I am saying is that rate needs to continue to be positive and out of 20% survivors many will not carry the survival gene. And on top of that, it isn't just one thing that kills a rabbit in your example, the climate, not finding mates, predators, disease and more all must be overcome at once. Survivors must overcome a wide array of adversity and succesfully pass on that combination of abilities and this needs to happen every generation.
Look at it in bits and bytes. For each adversity overcoming feature that a species has inherited, let that a be a bit set to 1. With 2 adversaries you have only two bits where only need one out of 4 individuals that has both bits on. For a realistic adversity of 32, you need 4billion bits all set to one. And this is without considering how a survival trait against one adversity can be a fatal trait against another. Now these bits need to be passed on, if one of them is missing then the only chance that individual has to survive is by pure chance they avoid that adversary.
Think of the endless adversities we face and overcome, you are saying for millions of generations, there has been an unbroken chain of survivors that kept overcoming a geometrically expanding adversity. Just a degree increasing in the global temperature causes entire ecosystems to collapse.
Survival is the exception, not the default.