I mean, that's what the dating site data seems to show. Here is an example. This could also be explained by women being more "selective" than men (as the title of the article implies)... but since attractiveness is a subjective quality, I think "Women are more selective about men than men are about women" is the equivalent of "Men are less attractive than women" in a heterosexual context.

Another statistic is that women tend to spend more time on improving their appearance than men (source, I only skimmed through that paper, but the two graphs at the end seem to support my point). So it would make sense that the demographic who puts more effort into looking pretty will look more pretty?

I'm not really sure why you would disagree with this? You can prove it for yourself by going outside and just looking at people on the street? The only way that you can ignore the divide in attractiveness between men and women is if you only consider celebrities, models, public figures, and so on, who spend a lot of money and effort on looking good regardless of gender.

I'm not saying male beauty doesn't exist or doesn't deserve to be appreciated. Or even that you as an individual have to care about whether someone is attractive or not (again, attractiveness is subjective). I'm just saying that the reality is that women tend to be prettier. It's100% a societal thing, maybe if history turned out differently, men would have been the ones who spend more time on their appearance.