Does the acceptance of the Talmud by the nation also apply to secular people?

This is a question I have often pondered. In principle, there is no logical necessity for this, since not every normative system operates in the same way. There may be a system whose acceptance is ultimately binding and prohibits abandonment. For example, a system of moral laws (the social contract). In any case, it seems that a distinction must be made between someone who abandons because he believes it is not true and not binding (there is no God or He has not been revealed), and then he abandons regardless of the question of whether it is possible to deny the commitment you have received (especially if there is a mistaken acceptance here), and someone who abandons even though he believes it is binding simply because he does not feel like it. I spoke about him above. I have no evidence for this beyond the halakhic determination that it is impossible to convert (there were opinions in halakhic that it is possible, but they ruled out around the 16th century and since then it has been accepted that it is not). I once heard of a statement by Chazal, "Esau Israel was a convert" – which means that he was the only Israelite who succeeded in becoming a convert. The argument of the Mudea Rabba in the Gemara Shabbat is made by the people of Israel and not by an individual Jew, and even with regard to the people it is rejected after the days of Ahasuerus and Esther.