I think we could go around on this for hours. The most cynical argument is that all forms of affection/stimulation are learned. Evidence for this might be that kissing is only a romantic gesture in roughly half of cultures across the globe ( https://hraf.yale.edu/romantic-or-disgusting-passionate-kissing-is-not-a-human-universal/ ) though, it sets aside the fact that kissing exists as a sign of affection, albeit non-romantic, in other cultures, especially ancient cultures. People get hung up on very old documents that mention a kiss, for example. Less cynically, it is important to note that kissing involves an intimacy and closeness, eye contact at some point, and those things are fairly common and intuitive. Wanting to be close and form emotional connections seems to be at the heart of it, and it makes sense that the cultures with larger personal bubbles would find kissing more erotic.
Honest question: do people who escalate to rather raunchy sexual practices find any pleasure in a simple kiss? (I'm now reminded of a scene from Monty Python's Meaning of Life that I won't link to because it could be slightly triggering) Is the idea that I'd even ask this question laughable to people who have escalated?
Intercourse itself, the kind that makes babies, obviously exists in every culture (except maybe the one we're creating through porn, and giving ourselves a pretty low replacement rate, but that's another matter).
*lots of triggers*
I guess it is the total connection and offering in sexuality that is key for me when making an intuitive call. For the life of me, I can't imagine receiving oral sex or a hand job (is there a more clinical term for this?) as being a form of connection. It just seems like assisted masturbation. Maybe because I'm thinking of it from her perspective; I can't imagine just staring at my own junk and deriving pleasure from it. I can only understand her appeal from the people pleasing aspect, in part due to what I mentioned before that I'm not convinced that the penis is actually all that erotic of an object to women. Men seem more interested in isolating body parts and eroticizing them than women.
Some sex acts could maybe be categorized as ways to get sexual pleasure, but keep the person herself at a distance. Anal sex might be very high on the sexual pleasure scale, and for all I know the colon is more stimulating than a vagina, but you're also not facing the person or really having to be attentive to her in any way except going about your business. At what point is your sex partner just a super realistic blow up doll? The word "dehumanizing" gets tossed around a lot, but I think we should all be keeping it in the front of our minds from time to time.
One thing I've noticed post porn is that the emotional/connection/closeness component is FAR more arousing than a porn addict would think it should be. We might remember it from our adolescence, and because of this we will forever associate it with childishness, but I'd propose that it isn't childish, it is just a little more pure and predates porn. At least in my case, I didn't get high speed internet until my 20s. Most of the world looks down on a guy who might get a little weak in the knees making and holding eye contact or standing over a woman's shoulder close enough to smell her hair (Joe Biden jokes aside). The fact is that these are pretty natural things, and things that get drowned out by exaggerated sexuality given to us by porn.
(One heck of a tangent, but for a long time people were talking in reboot about having the "super power" of being more attractive to women. My best guess has always been that it has been because of small things like being able to make and hold eye contact, not being strange and jittery and giving off weird perv vibes that has led to it. Women are programmed for the less raunchy aspects of sex more than men, and it would make sense that they'd intuit these behaviors as positive. Evolutionarily speaking, women play "baby roulette" with sex, and are more likely to seek someone who is husband/father material. You can imagine the soft sex guy sticking around playing with toddlers a lot more than the guy suggesting anal sex.)