Morals exist. It’s just that they are not high ground. This is because morals simply relate to interests, many of which are sexual.
Those who consider themselves moral nihilists but live in accordance with their biological and sexual urges are usually just opposed to current moral systems based on religion and sex-negative ideologies.
They do have a value system. It’s just that it has not been well articulated.
The Kreutzian value system is a comfortable death and, before that, during one’s lifetime, optimal sex.
For a true nihilist, this value system would be no better than that of a Catholic priest.
Evolution has resulted in men competing with each other for the most and the best females. Evolution has also resulted in women competing with each other, maybe not so much for the most men, but definitely for the best men.
These mechanisms will not be overcome.
Nature has driven men and women to compete with each other. But nature has also equipped men and women with the capability to act in solidarity for the benefit of all who act in solidarity, to first exclude and then overcome opponents. Such solidarity can, for example, create societies that allow an optimum of personal, including sexual, freedom in an atmosphere of safety.
But even a gentle, sexualized society will produce losers. And they will have morals. Other morals.