Guys, please. I beg you. All of my brofists if you provided a few example of what you consider extremely bad writing in the game. I'm not disagreeing, but I have to see for myself if I consider the same piece of writing as atrocious as you're saying.
The companions are typically quite annoying. People make the comparison to Critical Role and I think that's a good starting point of reference. Everyone in your party is super-special and most of them have utterly ridiculous special backstories. The catch is that none of them are very interesting, though obviously that's subjective. I quite liked Karlach and Astarion but nobody else really did anything for me. The worst part is perhaps their lack of integration into the main plot - I raised the example a while back of Lae'zel demanding you go straight to the creche, then following you in the opposite direction and never objecting if you skip the creche entirely.
I'd also suggest the main plot is quite badly written; the player characters' actions typically aren't well-justified and, because the game is actually quite linear despite pretending to be otherwise, there's often bits where you're either offered a fake choice that's quickly revealed to be fake, or simply offered no choice at all at a juncture where it would be appropriate to have one.
Dialogue is often smoke and mirrors, totally different player dialogue choices will lead to the same response from an NPC. This sometimes turns into poor writing as conversations start to feel a bit railroaded if you deliberately try to go off-script and pick options the devs clearly didnt want you to.
Villains typically have no depth. There is no convincing reason to side with the goblins/Drow in the first act, for example, other than to be an evil dick for no reason. This is by design, I assume; Larian set out to write something without complexity and to offer people a familiar-feeling adventure with clear good and bad guys, but you might still find it quite disappointing.
I sperg'd out about the brothel a while ago in the thread which I consider to be a particularly dire bit of writing, but that's probably due to my sensitivity towards the topic combining with the writers' obvious lack of care, and the protagonist being forced to voice a specific viewpoint (which
mostly doesn't happen elsewhere).
Other than that, for the most part the writing isn't bad, but it's quite shallow and is always in the service of a boring and mostly linear main plot. If you go in expecting an action-adventure without much to dig into, you won't be disappointed, but if you expect it all to make much sense and for people to behave in complex and convincing ways, the plot doesn't really offer that.
