Welcome to the forums Kappa Omicron (and cool pseudo by the way).
A couple of quick points.
The specific issue of not being able to act as a party during conversation has been reported many times. Although it probably took a back seat to other topics (e.g. Reactions) since the release of Patch 8, a couple of weeks ago. And now that I think of it, I may have seen this pop up on Reddit more frequently than here. But in short, no, you're certainly not alone in caring about conversations. And more generally, you are not alone in feeling that the game fails to deliver on the "party-based RPG" aspect, on so many occasions.
I'll briefly add a couple of points regarding the multiplayer experience.
- When your friend starts a conversation (and thus a cutscene), you have to actively opt in to experience it as well. Instead of having to opt out if you don't want to see it. In my view, that's clearly the wrong default setting. I can think of few cooperative games where I have to ask the game "yes please, show me the story as well, I'm not here just for combat and shenanigans".
On top of that, you have to be quick to opt in, otherwise you miss out the beginning of the cutscene. Not really appropriate in a turn-based game.
- When your friend selects a dialogue option in a conversation, you do not see what they selected. You have to either ask your friend constantly "so what did you say" (not an authentic tabletop or coop feel), or overlay the dialogue history (and miss out on the graphics).
Your point about not being able to use a party member's skills (e.g. Guidance) if they are controlled by another player is a good one though (and new to me, as I didn't playtest multiplayer since the so-called "Active Roll UI" was introduced in Patch 5).
