Is incest moral or not?

The feeling that it is immoral stems from the fact that in our country the word morality (meaning in Hebrew) is associated not only with harming other people, i.e. ethics, but also with a life of debauchery - i.e. a life of gluttony, debauchery, etc. - i.e. addiction to lust and the pursuit of fulfilling one's impulses (in fact, in the US, it is also called morality. For example, there is a morality department in the police force that enforces prostitution laws). Because there is also a feeling that a life of debauchery (in the language of aesthetic morality) also somehow entails crime and a violation of normal ethical morality. That is why the vast majority of Western countries also prohibit the sale of prostitution (except for four countries: Germany, Australia, Nevada in the US (because of Las Vegas), and one more that I can't remember). The sale and consumption of hard and even soft drugs are also prohibited in almost all of them. And indeed, this was also the main point of the dispute between Sparta, which educated its children in a strict education for a life of military modesty, and Athens, which educated them in the hedonistic life of philosophers and produced weak-minded and spineless people. And indeed, Sparta was at the forefront of the Greek cities that managed to resist the Persian occupation.

The issue of harming the family is only part of a larger issue that the integrity of human society with its human achievements, which enforces and encourages ethical morality (without which it cannot exist. Without it, there is only a jungle and no technology and spiritual life, etc.) depends on a life of order, meaning, and striving toward a goal, and not just a life of acting on impulses, emotions, and desires. A life in which desires are realized and not a pursuit of momentary pleasures. And I still really don't have a full explanation for why the abolition of aesthetic morality would entail the abolition of ethical morality, but I have a very strong feeling that this is the truth (beyond the trivial explanation that a person who is used to acting to fulfill his impulses will have a hard time stopping them when it comes to harming others, especially when it prevents him from fulfilling an impulse when it is one of the normal impulses he pursues the rest of his time. After all, people steal because they need the money to fulfill their normal desires that do not contradict ethical morality. It's not that people have a particular desire for the very act of stealing)

And I have never seen any liberal (including those who support the abolition of prostitution and the prohibition of drug consumption) who is willing to abolish the law that allows people to have sex in the middle of the street or even walk naked in the street. Even though in principle there is nothing immoral about it. After all, people also kiss in the middle of the street.

The enforcement of prostitution is because of the harm it causes and because of the perception that it is not done voluntarily and truly freely. These are moral issues in the usual sense.
As for street sex, it is a matter of disgust, not morality.

Prostitution has always been enforced only because of the damage it caused, but the damage it caused (i.e. the crime surrounding it) was due to the disrespectful (immoral) nature of the profession. Therefore, there were claims that it needed to be institutionalized. That was the case until the middle of the previous decade, when the progressive nonsense about prohibiting prostitution began because it is not truly done out of free will (which such a claim could be true for any evil choice made by any person in the world throughout history…). And in super-progressive Germany, prostitution is still legal to this day. The progressives ultimately not only remove responsibility from women, but also (in their arrogance) transfer responsibility for prostitution to the men who consume the women who provide it, because of their perception that women's society deserves privileges because of its victimhood and weakness. After all, even men who consume had sacrificial life circumstances that led them to consume prostitution instead of obtaining sex from girlfriends or women… It's about like shifting the responsibility for selling drugs from the sellers to the consumers who buy them…

In any case, a true liberal should not prohibit by law activities that are not immoral because of the harm they cause. It is equally possible to prohibit eating junk food or football games and other things that cause gambling that causes crime or to prohibit drinking alcohol, etc.’. Apparently, they also saw prostitution as a bad thing in itself (as with gambling and drugs) and the harm caused by it was the blow to the fetish for prohibiting it (as a sign and not just as a reason. Or a chest for the aestropi). And even in countries where prostitution is institutionalized, there are still problems of trafficking in women (from underdeveloped countries) for the purposes of prostitution, and this is probably caused by the lustful nature of the environment.

And besides, for a true liberal, since disgust is a matter of taste and not morality, it cannot be that a matter of taste should limit what people can do in the public sphere, right?

If we isolate ourselves and talk only about the prohibition of a man's wife as incest, then yes, in my opinion it is immoral even without the Torah, and this is where the destruction of the family structure definitely comes in again.