Your fundamental mistake is this statement:
the purpose of an organism is to pass along its genes through reproduction
Evolution does not actually involve "purpose" in any way. Rather, it is just the observation that populations with traits that more reliably produce descendants end up with more descendants.
With regards to humans, being really smart and flexible creatures has been extremely advantageous for us as a population (so far at least). One of the side effects of that intelligence is that we have a lot more agency in our choices than many other forms of life---and also a maddeningly huge amount of variation in our world-views and preferences (whether consciously chosen or otherwise).
That includes one's attitude toward sex and reproduction, and so it's entirely unsurprising that there are many people who choose not to have sex, or who choose to have sex but not to reproduce.
At the same time, no matter what your personal opinion on the sufficiency of our drives may be, it seems to be enough to motivate most others to have sex and children. As such, there doesn't seem to be anything selecting for that motivation to change, because the people who are insufficiently motivated to have children will not tend to have descendants, while those who are sufficiently motivated will.
Bottom line: humans are reproducing effectively and those who reproduce are evolutionary selecting for the status quo---the same drives that already motivate them to reproduce.