Modernity, although it would have also shaped your personality.
Nevertheless, in the time and place I live, I doubt that my male ancestors would have done any better in my place. Narcissism and self-centeredness are so normalized that the kind of man I am doesn't really belong. I think there are many men and women like I am who simply aren't attracted to the opposite sex in the form that they tend to take in modern civilization. I was just recently talking to a female relative of mine who has a similar perspective.
People are also less visually attractive in general. I've been at the beach a few times recently, crowded ones, and I noticed that there were virtually no attractive, beautiful, or sexy people like I remember. My standards are not extraordinarily high, btw. Over half of people were overweight or obese and the minority that were even close to being in shape weren't wearing anything particularly flattering. By the way, this is in California, not the middle of nowhere. I've met foreigners who believe that Los Angeles is full of hot people, and that was somewhat true at one point. Now, I'm not so sure.
Believe me, I appreciate body diversity, but everyone being fat and slovenly (i.e. unhealthy) isn't diversity or a positive thing.
Anyway, I think that people are just less attracted to each other in general. They've either abused their bodies to the point where they look a decade or more older than they should or they just dress like slobs. Or they dress in ways that signal that they aren't interested in any sort of serious relationship.
There's also just the general perception of globalized craziness. On top of not being appealed by emotionally immature partners (with no useful skills), why would I want to bring a child into a world where their way of life is going to radically shift several times in their lifetime? Why would I want anyone to live under technological tyranny? Or the consequences of humans abusing the environment?
People point to the "mouse utopia" experiment, but I don't think it's that. Technological inertia is what is bringing us to this point. Besides a little bit of HN and the occasional episode of 80's TV, I've pretty much disconnected from it all, and more people I know are disengaging. It's both a good sign and a bad one. If people are disengaging, that doesn't really mean that society itself is correcting itself. We're wincing at the wall we are about to crash through.