Another limitation of this game’s story is that it needs to work without any companions at all for custom multiplayer parties. That means the story has to makes sense with or without our companions. Mass Effect 2 cannot make any sense with its companions totally removed.
You make a very good point that I often don't remember, because I'm a solo player through and through for RPGs. The story must go on as it were, and it HAS to work without any of the companions, and all of them. ME had some disposable characters, but overall, you had a core group that you were with for a long period of time, and so the main story could involve them more. BG3, SH, as important as she might be, can't be completely essential.
I've seen reddit posts of a guy that didn't realize the companions were companions, and went on a solo rampage throughout Act I, basically killing/doing everything as Tav, solely because he's so used to having party members forced on him. The game has to work for that type of player as well, and it does.
