The cynicism is assuming that people are following a motive which leads them to promote their own genetic fitness.
They're not. This motive isn't explicitly represented anywhere in their brains, for the most part. People usually don't, consciously or subconsciously, worry about whether what they're doing increases their genetic fitness. They follow a variety of emotions - fear and anger, love and friendship and loyalty, hate and curiosity and a host of others. Now, it's quite likely true that those emotions are what they are because, in an ancestral environment, they promoted genetic fitness. But the link is indirect. If some of them no longer promote genetic fitness, that's not going to make them go away. People can still fall in love and enjoy sex even when they consciously know they are infertile or when they decide to use birth control. If there are other things to do in the modern world which would promote genetic fitness even more, those emotions aren't going to magically appear. Guys don't fall in love with sperm banks.
The cynical, and incorrect, part is in assuming that "genetic fitness" is actually a motive of any present-day human.