I’m certainly with you in wishing the game always allowed us to pick which party member should talk (apart from possibly the odd situation where that wouldn’t be appropriate). But given this has been a popularly requested feature since early access I suspect you’re unfortunately right that it’s not likely to appear now.
Of course, it ain’t over until patch 7 is out, but I am resigned to disappointment on that front. Though I’m all for banging the drum once more as even if the ship has sailed for BG3, I can hope Larian will design this into any party-based RPGs they develop in future.
