Why is 23 partners a red flag?
Like, having 23 partners because, excuse my french "Elle voulait simplement baiser à tout va" is just fine (tm), they did what they want, and that tells nothing else about them that the fact they did what they enjoyed doing.
On the other hand, if they were looking for the one true love and thought they'd find it in 23 different people, it may reveal something else about them..
That they prefer a type of partner which does not align with their goal.
Or that they are a terrible judge of character.
Or that they are easily manipulated in general.
Those may be red flags in their own right, if those traits are undesirable to you.
People go out, have short relationships / flings, one night stands without any intent other than have fun. It's fine. Let people have things.
I'm making no assumptions _about_ intent.
I'm saying whether it's a "red flag" depends _on_ intent (which is then assumed to be known, at least internally by said person(s)).
I'm making no correlation between having causal sex and the attempt to establish a long-term relationship, I don't know how I could more explicitly define those as two different goals.
Maybe if I write it in a more simplistic (albeit, less precise) way:
* Many relationships may likely a red flag in a person who's seeking long-term relationships (ie, they're trying and failing very much, they're probably not a very good partner, or has very good judgement).
* Many relationships are not a red flag in a person who's not seeking long-term relationships (they're doing their thing, and all is good, as long as you're aligned with that).
What if there is a diamond in a pile of garbage ?
If someone legitimately enjoys casual sex AND has no baggage OR some kind of dark triad trait.. is that sort of person common, or rare?
As for the act: If there's no harm to anyone, its great. ON that light, casual sounds logical. But is your own body just another playground ?
Throughout history, there are numerous records of temperance being a virtue and hedonism being a vice. Coming from all sorts of corners.
Its not as clear cut.
For the same reason you don't want to deal with a client who's churned through 23 other contractors before you either, or an employee who's held 23 other jobs.
They're either high-conflict, non-committal, fishing for something and not finding it, using sex as a coping mechanism/don't take the act itself seriously (won't be the last time you hear them tell you sex with strangers "means nothing;" just wait until your first big fight). There's also disease risk (mainly herpes).
Nothing about a body count that high signals stability or commitment. I'm sure plenty of people can and do change and can commit and be stable; we could be friends but they are not people I would bet the rest of my life on. The only three people (two males, one female) I know with body counts that high all got caught soliciting or banging children decades later, so my experience with this is admittedly subjective.
For much of history (pre-industrialization) men weren't often as tall due to begin with, due to more prevalent nutrient deficits. Additionally, rather than trawling a site with thousands of men you were largely limited by your location for potential suitors, so you simply couldn't be as picky (if you had a choice at all, as women often didn't).
I generally find that people need to be much more careful when discussing these kinds of topics. People are very quick to attribute certain attributes of desirability to biology, and there are no doubt common threads amongst humanity, but there have also been enormous swings in social trends that have ignored these factors.