Sex is ubiquitous in today's western world. Sexual promiscuity is not only condoned but encouraged. Some argue that this is just the way things are naturally supposed to work. Actually though, this wasn't the case for a long time. People actually invested little time and resources dealing with sex. It was pretty much took for granted. Most people would eventually become of age, seek a partner through networking in communities (a small village, the church etc.), get married and that was pretty much it. They'll eventually move on to deal with less worldy and animal-like aspects of life rather than sex. It would play a small part in the rest of their existence, and mainly for reproductive reasons.

Ironically this glorification of sex happens in a time where many people are having less sex than their ancestors used to (there are many studies you probably already know, I'll just link one)

https://www.theatlantic.com/magazine/archive/2018/12/the-sex-recession/573949/

By the way this is absolutely consistent with modern sexual dynamics, since of course when a resource is scarce, it becomes fetishized.

This mechanism also features a key characteristic of capitalism, which is unequally allocating resources: on one hand you have attractive people who are so awashed with sex, and take so much pride in succeeding at something so glorified by society, that they make it one of their main focus in life; then you have normies who delude themselves into thinking they'll eventually get to live the same life as attractive people if only they try hard enough and invest enough time/money; and finally on the other spectrum we have incels who are completely deprived of sex, and thus end up making something so worldly, something they were supposed to take for granted, their main source of pain, misery and motivation (or more often, lack thereof)

Quoting from Marx's "Economic and Philosophic Manuscripts of 1844" regarding the estrangement of labor in the factory based system of production:

As a result, therefore, man (the worker) only feels himself freely active in his animal functions – eating, drinking, procreating, or at most in his dwelling and in dressing-up, etc.; and in his human functions he no longer feels himself to be anything but an animal. What is animal becomes human and what is human becomes animal.

Certainly eating, drinking, procreating, etc., are also genuinely human functions. But taken abstractly, separated from the sphere of all other human activity and turned into sole and ultimate ends, they are animal functions.

There's only a finite amount of resources (time, money, intellectual capabilities) one can dedicate to a given number of activities. If a mundane activity such as sex ends up absorbing a hefty share of them (either because you're good at it and like indulging in it, or because you can't get any and won't stop brooding about it) there will be less resources to dedicate to something else (e.g. questioning the status quo)

Obviously we now live in a post-industrial society. People are now consumers first, rather than producers. Capitalism has thus switched from exploiting labor, to exploiting consumption. This is where the commodification of sex comes into play. Sex being promoted, advertised, fetishized, and unequally distributed just like any other commodity, only broadens the spectrum of consumption, and the broader it gets, the more there is for capitalism to exploit.
Labor -> Consumption -> Sex.
As a consequence, stemming from the estrangement of labor, WE CAN RIGHTFULLY TALK OF ESTRANGEMENT OF SEX as the main tool to degrade mankind.

What is animal becomes human and what is human becomes animal.

[A picture of Karl Marx, Lenin, Stalin, Mao, and then Elliot Rodger]