Do you believe dating sims negatively impacts gamers from dating real women (seeing as there has been discussions regarding Japan's decreasing population with dating sims being partially to blame)?
Who cares? It's not some sort of moral imperative that we seek out women and breed. If people are happy playing dating sims rather than actually dating, that's a good thing, not a bad thing. It means more people are happy. Good for them.
As for the larger question, I don't play them myself unless there's more to it than just dating a bunch of shallow women with cute faces. There are VNs I really enjoy, but a lot of dating sims in particular seem to be shallow crap made for very lonely people. What's the point of that? I can't love someone with a flat personality that never learns or grows. Part of what makes people great is our ability to overcome hardship and learn from our experiences. Dating sim characters, they usually don't do this. They're flat in every way except anatomically.
Now, if the characters are interesting or the story or presentation is interesting, then I'm more willing to give it a shot. That's been the case for at least two that I can think of, and in the end, I did really enjoy myself reading them. However, in that case, it's not because it's a dating sim, it's because it has something else that interests me. I'm no more likely to like a character in a dating sim than I am to like a character in any other work of fiction. In the end, it comes down to whether it's well-written or not.
I kind of wish these kinds of things were enough to satisfy me. I'd probably be a lot happier if that's all it took.