Simply put, I think dating someone with a kid is difficult unless you have your own or have had your own. It adds complexity to a relationship tht should be about you and the man/woman you're dating that doesn't need to be there. If you're a single that has never been married and/or with children it will only exacerbate the problem for you too.
I also disagree that in any way your place should be in anything to do with parenting. You're a person that is dating someone with a kid, there is no real commitment there yet. Even if you ended up marrying someone with a child, step parenting is a contentious subject then, how much more is it going to be questionable that you try to be an authority as just a girlfriend ?