You can't just blame the actors when it's a line here and there. The director and editors are complicit, as they might go for the blandest or most scenery chewing takes.
Yeah, but would a director tell any actor to do what McCready did as Dr. Carter? He was fine delivering his recorded warning, but the death cry was cringe-worthy. Again, IMO, that was the one and only bad acting moment in an episode played seriously--often grim, with great effect.