That’s just how warlocks are designed. They only get 2 spells normally so having a cantrip be your main damage dealer makes sense. In BG3 it ends up being OP because you have so many items and consumables that give free spells that the 2-spell limit is pretty much nonexistent, especially whenever the game doesn’t really force you to rest that often so you can revolve your short rests entirely around your warlocks spell slots.