In the spider cave it took the 30 spiders about 10 minutes to finish each one of their turns but I guess the combat is too slow.... Hi welcome to the BG3 forums have you even played it?
Again, I mention specifically in the post that this is nothing to do with the AI "thinking" lag, obviously that is a bug/issue - I'm really talking about player turns, which is the opposite side of the same coin you're describing here. Our turns are really quick, but the AI takes longer because generally there are more of them and they spend a good few seconds each "thinking" (it says at the top of the screen).