I think the point is that the evolution of human intelligence reached a point that enabled us, over evolutionarily short timescales, to develop an environment (social structures etc.) that broke evolution as it was – the meaning of "fittest" is now rather arbitrary in human context.
I'm not sure it is arbitrary, just different from what it was a hundred or a thousand years ago. There's no real survival differentiation in modern society, and while classically beneficial traits like physical fitness and intelligence do help with finding partners, most people are able to do so regardless. The other big difference now though is that people can have sex without choosing to have children. So istm the most successful traits from an evolutionary perspective at this point are those that encourage a desire to have more children. (If there's a genetic predisposition toward religious adherence, that's a likely example.)
