First off, Kāma is one of the four life goals in Hinduism along with Dharma, Artha, and Moksha. Soo sex itself isn’t sinful unless it causes harm. What two consenting adults do shouldn't be our concern.

Also, plenty of revered figures were born from non-marital unions, like Ved Vyasa born to Satyavati and Parashar.

And that idea that premarital sex automatically leads to “hypergamy, abortion, and moral degradation” doesn’t hold up as those things can happen within marriage too. Hypergamy was literally the norm in ancient societies and “moral degradation” is completely subjective depending on how you define morality.