This question is absurd in a D&D context.
No, it's not. He made a legitimate counterpoint.
Your problem seems to be that you can kill anyone for extra exp even after completing quests with them exploiting the system for extra exp rewards (which may be a legitimate concern to a certain extent), not that you can talk to them after the kill (which is a separate matter).
Incidentally, in the overwhelming majority of cases the game actually doesn't let you interrogate characters you are directly responsible for killing (they in fact "refuse to talk to their killer") so there's that.
BG3 is not going to contain everything in 5E. And, many of the things that are "included" have been or will be altered significantly. So, there is quite a lot of leeway for Larian to choose if and how to implement this spell.
And it's not really clear what point you are trying to make here, on the other hand. Are you saying that the spell shouldn't just be available at all, by any chance?
This is a terrible argument. I might as well just play a different game, then.
"If you don't like it don't use it" is indeed generally speaking a poor argument.
It doesn't change the fact that you are identifying a genuine problem (an exploitable reward system) but failing badly at identifying the culprit or the possible solution (the "Speak with the Dead" spell and its removal).
