Honestly, I don't think a bland image like Halsin could outshine anyone, no matter what Larian does with old characters, even though they PR him and shove him in the player's face as much as they can. Maybe they're trying to make him brighter than Jaheira, "Look at what a druid we have, strong like Minsc and a druid like Jaheira". He manages perfectly well to only provoke anger with his brash behavior and all the threesomes, thus cheapening Orin's kidnapping quest (which should, in theory, be perceived as a misfortune, and, the player, nervous and worried about their companion, should strive to get him/her out as soon as possible, becomes a grace: "Oh, my dear enemy, thank you, now I won't see him in my camp again until the end of Act 3!" and Orin's quest is postponed to the very end of the game).
Ironically, the Orin kidnapping thing is taken straight out of BG2 but implemented pretty poorly, when you first see your Romance disappear into thin air after Bodhi's dialogue, you start sweating bullets... (unless you are romancing the "A MAZ ING" EE companions that just "... you thought i'd need to be saved? I DON'T NEED NO MAN/WOMAN")
I've seen Viconia disappear so many times i've lost the count but it still gives me the same exact feeling of urgency every time, it doesn't matter that i know she's just a few chambers away under the graveyard.
The way you also have to carry your Romance's body afterwards, running like a madman/woman to Amaunator's temple and the dialogue at the altar also really add to that... solidifying the fact your Romance is really important.
I really don't think Larian is trying to actively teach any moral lessons with the game. They have their own perspectives that are appearing in the story, but that happens with every story. But I do find it baffling why they turned that druid immortality thing into a ritual when it's meant to be just an automatic thing that happens. However in defense of Karlach not asking for the ritual to be done to her, the way it works is that druids are ageless, but they can still be killed. So it wouldn't fix the engine. And doesn't Jaheira say that it's a thing for old druids anyway? I've only seen the scene once so I don't remember it very well.
Yeah, it's druid exclusive and causes you to age 1 year for every 10 that elapse... not real immortality, that's achieved in other ways.
But the annoying thing is that it isn't an "old druid" thing, it's a reward Nature bestows onto the most experienced Druids for their devotion(In the form of primal energies coursing through their body)... no ritual required.
About the moral thing, i think it's more a matter of them trying to elevate their own characters and convince people to hate the old evil characters(they succeed with most of those who'd never played the originals or weren't really invested/didn't know their characterization real well)... they even shit on the Dead Three by having Jergal chastise them and imply they will never be relevant again. Bhaal and Myrkul don't even get stronger despite all of the death and destruction that happened during the campaign.
Jergal is also wildly out of character and acts as a sort of moral validation for Durge "oh you made a life for yourself, separate from being Bhaal's chosen... uwu"
*Looks at the fact Quasi-gods can't bestow power, and at how Jergal's dogma includes "Never prolong life unless it furthers the end times", with him being Kelemvor's scrivener and knowing everything about anyone who dies but also making sure Kelemvor doesn't act too kind*
