A lot of sex is not that great and therefore any overall reduction of sex may be a good thing, depending on which kind of sex we're having less of. Maybe a lot more married women are not having sex with their husbands, which traditionally was not always an option. Maybe young people are rushing less into big relationships, and so without a steady partner regular opportunities for sex are reduced while at the same time more bad relationships (and marriages) are avoided. Maybe people are engaging more in non-intercourse sexual activity now that access to information about kinks and fetishes is universal.

I say, let's stop stressing over the quantity of sex and instead focus on the quality of sex. We should want people to find partners where they can have open communication, and where they have similar desires and where they can share in enthusiastic consent. But this idea that "more penis in vagina = good" doesn't hold up to any scrutiny.