I often wonder that since nature can't control wholesale population with plagues anymore if it has created a scenario where it will just make people desire sex less as a sort of backdoor population control.
But then I'm not so sure that nature is that smart.
Also alot of people are getting their needs met digitally now and going out and finding worthwhile people to touch is a chore, it's messy, in every sort of way. It takes time, money, and energy to live a promiscuous lifestyle for not much more thrill than can be had binge watching something or scrolling a screen.
In the pre-digital past it was either sit at home and watch one of your three TV channels or go out and get laid.
Not that I think all of this is healthy because as the OP said, the desires are still there, and I think that now people are focusing those desires on a sort of bland workism. Throwing themselves into their careers as a distraction from their old school desires.
Hence we are seeing more articles like these:
Yeah I think nature is pure chaos so this idea that it's somehow levelling things or whatever seems like an anthropomorphisation akin to re-building God (and I see this attitude from social Darwinist atheists a lot
, you'd be surprised how many people worship evolution/nature as a God that can do no wrong or can't be questioned. Replace the words nature/evolution with the Abrahamic God and you'll get different groups of people echoing all the opinions Christians and Muslims have about God.) The truth is, many of it's effects are and always have been dysgenic.
Anyway in research population density tends to be focused on less than some more politically motivated angles, but there certainly is a connection that has been found when they've examined it between that and it makes sense because it has an impact on fertility for every other species and even microbiology.
I'm not convinced about technology being as important as population density because you can see in other mammals they'll sit and do literally nothing at a certain point and also self harm, which seems to be what many mammals do - pain is the default stimulus replacement for boredom not sex. Might also explain why everyone wants to start a war (though many things contribute to that drive including reducing outgroup members.)
You need the illusion of space and possibilities for resource acquisition - not being created in the 'let's make flats the size of a taxi cab
edit: but there are a lot of intersecting factors on a higher level yeah, often stemming from the abundance of people in the first place so some examples:
1. easy access to porn/entertainment
2. female education/intelligence
3. A socially constructed system where 162 billionaires have the same wealth as 50% of Humanity.
4. sociosexual orientation
edit again: More controversially certain elements of how some people's sexualities are working now kind of resemble prison environments, but it's not a large enough group and there are too many confounding variables for me to conclude that that pattern is necessarily meaningful. I've found some really peculiar anecdotes though.