This right here.
The problems with the Origin system are very subtle but systemic on a deep level. Most people don't realize what it does to the narrative at first. I didn't when I played DOS2 as my first serious cRPG, until I explored the genre and realized how the system just made the DOS2 companions and the overall narrative extremely dull in comparison.
DOS2 companions, when they interject in conversations at all, only do it during their personal arcs, or only have very generic quips about what they would decide to do in a particular situation. There's insane amounts of missed potential here. Probably the most interesting interaction they have between each other (or the ONLY inter-party interaction I can even remember, for that matter) is when Sebille and the Red Prince have a brief scuffle about Sebille assassinating the dreaming lizard towards the beginning of the game. But it's telling that even there, they don't confront each other about it at all on their own, they just complain to you to hear what you think, and then this never gets brought up again thereafter.
One would think that Ifan would have things to say to Sebille about her being the Prime Scion and the potential future of her people, given that Ifan was indirectly responsible for nearly genociding the Elves. Or that Beast would have advice on how to govern for the Red Prince, for when he and the Princess assume the throne of the Lizard empire in the future, lest he end up with rebels like Beast making life hard for him.
I guess what I'm saying here is that not only does the origin system come at the huge detriment of custom characters, Larian's specific handling of it ALSO comes at the detriment of the actual development of the companions and the party banter that can reinforce said development. Not only are the origins clashing with custom characters in importance, they also clash with each other in the end.
Alexander could have been a secret companion that could have joined the party at the end of Act 3, instead of being immediately killed off with the obvious betrayal by the other antagonists. He had the potential to be a very popular and memorable character and would have been THE big spoiler/plot twist of the game, because if there's one thing that mass media likes, it's former enemies turning into allies. He could have also come with such a hilariously overpowered kit that he could have attained the same level of notoriety as Thunder God Cid from Final Fantasy Tactics. But the Origin system combined with the decision to kill off all inactive party members at the end of act 1 made this impossible. Imagine what Alexander joining the party and going through actual character development, along with the lack of the awful design decision at the end of Act 1, would have done to improve the highly lambasted narrative of Act 4. Imagine him confronting Lucian at the very end of the game and realizing just how badly he had been played by even his very own father the entire time. When you really think about it, it's clear that everyone trashing how Act 4 was constructed is actually a direct consequence of the Origin system and the end of act 1 culling, because Larian at that point had massively written themselves into a corner.
People fear that BG3's narrative will fall apart later on with this historical context, purely due to entirely avoidable gameplay design decisions baked into the game's core.
Don't underestimate this deep dive comment into Dos2's design philosophy.
The very important aspect of the system that origin opposers
Sometimes forget to mention is that even if the origin system didn't hurt the custom MC at all, it is still very harmful to the focus of the story and the party dynamic.
Luckily for me, Saito already gave many dos2 examples so I don't have to delve into that.
I can just say more generally, that the way the origin system works creates a situation in which the game has no real main character, whether you are playing a custom or an origin character. This fucks up the way characters in the world treats your group and how your group members treat each other.
