But I also think that dialogue should be efficient. "A good screenplay is an efficient screenplay." is something I once heard and that I agree with. Dialogue should have a purpose and ideally achieve several things at once.
Dialogue in real life is neither efficient nor multi-functional.
People can be verbose simply because that is in their nature. As can people be prompted to talk more by being engaged by others.
Dialogue is simply a means for communication. The depth and breadth of that communication varies with people and situations.
Of course, the thing to keep in mind for games is that dialogue often happens in "Dialogue mode" due to the need to facilitate giving players choice of responses (Meaning both give them time to read the options and decide and also the UI for actually picking a response) which should be minimized. But options are the bread and butter of RPGs (It's how you go about allowing someone to "Role Play")
The clip you linked does none of that, its only purpose is for the player to feel more important because they can make a selection - what I flippantly called a desire for the companions to fawn over your PC. It's not something I consider very valuable because to me it's basically bloat, that I am stuck in menu for. I hope this explains why I do not generally agree with you about more content.
The clip is trying to highlight that Morrigan is directly referencing the player romancing Alistair. Rather than a "Generic romance dialogue"
It being tied to a "Dialogue Mode" is not indicative of reactivity... It could have been done as banter dialogue (Much like how Karlach will respond in a similar fashion to Morrigan here when you spend the night with her at the Tiefling party, she'll mention that Shadowheart seems happy)
But the crux is that the companion character is making a response to a specific action.
So when I think about reactivity, I'd think about what would need to be explored further or add value if it was
In general, there's 2 kinds of reactivity to mention.
There's direct reactivity. Wherein companions chime in during dialogues to add their opinion to what is unfolding. For example, when a companion gets a temperment modifier from a dialogue option, they'll actually say something about it then and there instead of just silently watching (With them
maybe provoking a dialogue later, such as Karlach and Wyll talking to you if you agree to attack the Grove)
Then there's situational reactivity. Wherein companions will remark upon and alter dialogues based upon actions taken. For example, how companions respond to you after you've eaten a tadpole (With them having new greetings and sparking dialogues from Gale and Astarion)
Neither necessarily adds more dialogue modes, but it simply alters ones that exist as the player goes through the game. While providing benefits from doing so:
The former makes companions feel like they're relevant in dialogues, it also would help provide more insight into their stances and characters. Knowing
why companions are reacting in such ways provides more information than just the "X liked/disliked that!" (It also allows the conveyance of such messages immersively. Instead of having meta pop-up text tell you, you actually get to see the character react in real time). It can also lead to more fleshed out experiences, instead of it being a ping-pong of "MC selects dialogue > Other party responds" there can be actual discussions occuring between companions and NPC's between MC choices (And allow for branching dialogue paths where you choose to direct the conversation towards your companions or the other NPC)
The latter provides long term development for companions. It makes them feel like they are actually experiencing your actions instead of just being cardboard cutouts with specific dialogue flags. It brings your character into the world as things they do are being noticed by those they are close to. This is also where the major complaints in this thread about "Relationships" come in, whereby people expect that a full approval and romanced character would have their dialogue altered to reflect the fact that the PC had gone out of their way to be extra nice to them to get that approval and actually engaged and kept with a relationship. (It is also here that the major flaws of RPG "Romances" are shown, with the complete and total lack of any reaction to being in a romance outside maybe being able to select an option for a kiss if you talk with said companion)
