My issue with them in Divinity is that it felt like you got more of a story if you played the Origin Characters over the Generic one.
This doesn't seem to be an issue in BG3.
I don't really see WHY we should be allowed to play the companions as a main character. It seems a little pointless to me. Which is why I don't really mind that we can. I won't use it, but to each their own.
There is a tradition for premade characters in DnD though, it's done in some modules, but rarely do they have elaborate backstories. Usually it's there for the balance and the stats etc.
But again: I won't use it, so why do I care. It seems they know that custom characters is the main concept here.
I saw someone mention that they'd like personalized quests based on background you choose. I don't think I'd like that, as it would set my characters backstory and personality in a sense. In 5e the backgrounds are mostly there to help you write your backstory, and also give you some suitable bonuses. I'd like it if it gave some conversation options, but not really much beyond that.
I like that "my story" is written though gameplay choices, not by someone at Larian before the game starts.
What I hope Larian don't do is "lock" the companions full story to a playthrough with them. Part of a companions job is to give you a side story that you help that character out with as part of your main quest, and the Main Quest is YOUR story that the companions help you out with.