As it is now, to replace companion A by B, you need to talk to A, click through the dialogue options to tell to go to camp. Then, go back to camp, go to character B and ask them to join. This is really tedious on repeat playthroughs
It used to be the case, but not now. Now, you can just ask the new companion to join and then you'll get the option to dismiss one of your current party who will go back to camp. You'll also get the option in dialogue to replace one of your current party when a new companion wants to join you for the first time, if you already have a full party.
"You may call it 'nonsense' if you like, but I've heard nonsense, compared with which that would be as sensible as a dictionary!"
