There was a bit of stat reactivity in BG2, don't think there was a whole lot in BG1, but you're right that the story didn't go out of its way to change based on exactly what race and class and stats you picked. That's not really the point, though. The point is, there was one protagonist and only one protagonist and that one protagonist was the undisputed fulcrum of the storyline.
It was not a story about "some people", it was a story about one person and that person's fate as the person reacted to the world, grow, and happened to various people and places. The person would run into other adventurers, maybe spend time with some of them, maybe perform epic deeds alongside them, and maybe their paths would separate permanently or temporarily, and maybe they would stay together. But it was always about that one person. Charname.
Narratively, it feels different from writing a story where there's no chosen one and literally any from a bunch of dozens or hundreds of people with special tadpoles could take turns to be the main driver of what happens. It doesn't feel as focused. This is probably fine in an MP context, but if I'm playing a single player role-playing game then I expect to play an adventure about my character. Particularly in a D&D context, which is all about making "your character" rather than "min-maxing a toon".
And that protagonist was for the most part a [generic charname]. The narrative never made me care enough about the main character, the way I for example cared about the Nameless One. If this was a book or a movie, I'd not bother finishing it. Fortunately, as games the BG saga had more than the boring protagonist, like the exploration and fun combat.
