The BG3 companions have quite a bit of potential, but I worry a bit in that a lot of their appeal seems to be frontloaded into the more mysterious parts of their character arcs rather than anything you actually see them doing while they're in your party at the moment. The lack of party banter between the different members of the party speaks to this quite a bit. With the exception of Shadowheart and Lae'zel, they feel like they are seemingly being designed like completely separate entities rather than major pieces of a larger whole. Sadly, if Larian insists on going through with the highly implied 'all party members not in your active party at the end of act 1 will die for plot reasons' thing just like they did in DOS:2, it basically removes a lot of the future incentive for the writers to even bother putting that much effort into inter-party dialogue for the later phases of the game, when most players have no possibility of seeing the majority of said banter in any given playthrough with half or more of the potential playable cast already dead about 1/4th-1/3rd of the way into the game.
There is another cRPG, Pathfinder: Wrath of the Righteous, that is planned to be released in early September (specifically the 2nd). Judging from my experience beta testing it, the party members in that game basically do everything you described that BG3's characters are lacking in (along with one other thing you haven't mentioned, the game's NPCs and enemies actually acknowledging the existence of the party members instead of just the lead character, sometimes resulting in brief conversations between them). The major downside is that not all of their lines are voiced throughout the game, and the game is hardly cinematic, but I find it's largely a question of budget more than anything else.
I recently recorded a demonstration here... Be warned, it contains end of chapter 2 spoilers for Wrath of the Righteous.
Timestamps for reference...
- (0:36) Arueshalae (a defected Succubus Ranger trying to go on the path to redemption, currently in the beginning stages of a romance with my MC) interjects in the conversation. One of the antagonists directly addresses her and the two have a brief conversation. - (1:29) Lann (mongrelman Monk/Zen Archer has a general interjection. He generally favors self-depreciating humor as a coping mechanism. Not going to elaborate here.) - (1:49) Seelah (Paladin) interjects with an attempt to convince one of the antagonists to defect back to the party's side. The two have a brief conversation. - (3:35) Ember (Witch) interjects, only for another party member Camelia to respond directly to her instead. Then one of the antagonists responds to Camelia's rebuttal afterwards. Camelia's unique dialogue (and Staunton's following comments) here do not trigger if Ember is not in the active party. There's a few instances of party member dialogue in this game that requires specific combinations of party members present to see them, and there's potentially a lot as there are 10+ known party members right now, not including any additional secret companions. - (5:22) Another general interjection from Lann.
(By this stage in the game, I had 4 other companions outside of the active party, and they all most likely had something else to say here if I were to bring them instead.)
Since it's unlikely that BG3 is releasing anytime within the next year, the writers have plenty of time to see what WotR does in regards to its companion writing in order to steer the BG3 companions towards a better or more immersive direction.