FEASIBILITY is the name of the issue here, it's not like the idea that people would like it didn't occur to them. it's that "voiced main character" and "main character can be 35 different things" are two design principles that at least at this point in time are fiercely at odds with each other.
In an ideal world I'd like both of those, but having thought about it I think I slightly prefer the freedom to define my own character. I do like the occasional bits of speech to add in a bit of personality. Maybe one day the technology will exist to create the variations we'd want with AI, but I think that's a long way off. And even then, how would you control it? Will it be fun to tell the game whether you want it to say that line neutrally, enthusiastically, nervously, sadly? I'd like to see it if someone works it out, but from here I don't know how it would be done. It's not that imagination is in conflict with a CRPG: they enhance each other.
My brother, who's playing BG3 at the moment, told me that BG2 doesn't even have all the NPC dialogue voiced; and he thinks that allowed them to have more dialogue options, particularly related to romance. I can't say for myself because I haven't played it yet, but a fully-voiced protagonist certainly wouldn't help that. Even if I've played some very good games that
do fully voice the protagonist. They tend to have fewer options than BG3 did.
