Well, there are only five companions and you could be one of them ( If you are an Origin character) So you can save three or four and only one or two are left behind in the end.
In the full release there will be 9+ companions. So we would have to leave behind most of them, not just one or two. (Note: 9+ companions is a, I think reasonable, guess)
Personal tastes aside, that is the same already done in many games, the two already mentioned, the first POE where Calisca dies in the prelude, the two Grey warden recruit companions that die in DaO and daO: Awakening, Thrask the soldier that cannot escape the Endar Spire in Kotor with you, etc etc etc.
I'm sorry, but you can't compare the two Grey Warden recruits to BG3 Origin companions. The wardens are forced upon you, will always die, are only there for a single mission, and you can't meaningfully interact with them. *Most importantly, the death of these recruits does not limit the other companions you can collect throughout the game.
