If you go by pure content, you're might be right. However, according to an interview with Swen that I saw once, a vast majority of players actually choose to play custom characters in their first playthrough (I dont remember the exact interview rn, but if I do, I'll post it here later). If I remember correctly, that statistic was from a DOS game, and I can't imagine it being different with BG3.
So custom characters do have appeal - to me personally too - and I think it is literally because this is a role playing game, a D&D game, and in such a game you usually play your own character whos backstory you came up with yourself.
