>Having kids is one of those intense types of experience that are hard to imagine unless you've had them. But it is not, as I implicitly believed before having kids, simply your DNA heading for the lifeboats. But it is, because your entire biology has evolved for billions of years with the sole purpose of reproducing effectively. No amount of "I feel like I enjoy it" negates that it is programmed into you as an organ…
I think "simply" is an important word in that sentence, and when I read "is not ... simply your DNA", I read "simply" as "merely". He's saying that, sure, there is a biological compulsion involved, but there is also more to it.
The kid is a human being you can have a meaningful relationship with. They will do or say things that are interesting or worthwhile or significant in a way that's not really connected to the fact that they're your kid.
(It can be compared to a romantic relationship. Are there hormones making you want to be with a romantic partner because you like their looks, etc.? Absolutely. But on top of that, you can have a real friendship with a romantic partner where you have shared interests you enjoy pursuing together, you have interesting discussions, you support each other, and so on.)
On a side note, some parents can only see their kid through the lens of parenting. They rarely or never connect with their kid on the human-to-human level, and every thought and interaction is on the parent-to-child level. Maybe they just haven't thought in those terms, or they're afraid of undermining parental authority by being too much of a buddy, or their sense of parental duty dominates their thoughts, or maybe they can't connect personally to anyone else either.