It is true that some people are not really cut out to be parents. But unfortunately it is difficult to tell whether that will be you or not. I see people looking at comments in threads like this and then chiming in with sentiments along the lines of "see, this is why I never wanted to be a parent." There is no way to know that, and such statements strike me as cope. Becoming a parent changes you, but you won't know how until you do it. There is a lot of biology and psychology in play, for certain.
As I tell my own kids, however, be careful because you only get to become a parent one time. Cannot blame someone for opting out of the risk, even if the counterfactual is that they would have been amazing parents with amazing children and been much happier.