the kind of phenotype that will produce the most offspring

That's only beneficial when your children are an asset to community survival. Predators tend to produce fewer offspring, because every new member of the predator cohort is an eventual rival. Prey species benefit from large populations when the populations' role is to terraform territory or otherwise synergize with their kin. This is a big fundamental difference between animal and plant reproduction, since plants generally benefit from more members of the species in the immediate area while animals have a soft ceiling on their population tied to how much food / shelter is available.

One could argue that the human habit of terraforming and the synergy enjoyed by a large population of active brains in a small area puts us more in line with plant species than animals.

The Survival of the Fittest trope is flawed on a whole host of levels. The idea that you want a small number of apex predators as a survival mechanic neglects all the instances in which a very large number of prey species perform significantly better.