I posted about this earlier, and I do agree that if they are going down the commitment path - it should feel like a powerful narrative decision and not a "let's get rid of the inconvenient companions handwave" we had in DOS2.
Everyone that isn't in your party immediately dies to plot device #23 so that you can safely forget about them the entire playthrough? Feels like a bad design choice used to "improve replayability".
However, if characters you don't take are re-integrated into the story as proper NPCs - i.e. you leave Astarion behind and he's now a NPC in the Cazador quest line. Or Lae'zel joins up with the Githyanki hunting squads. Okay, I'm a little more open to that. Extra points if how they act as an NPC is influenced by your relationship while they were in your party.
