So here's footage of a current late EA boss fight where I pretty much combine a lot of reactions and ready actions together to counter the boss' primary mechanic of casting Darkness, taking advantage of the fact that he can only attack in melee to bait him out of the cloud to take several readied stabs to the face. As you can see, there is a lot of forward thinking and prediction that goes into this, an entire dimension of tactical thinking that exists purely because of the existence of reactions and ready actions. I probably end up acting during the enemy turn just as much as I act during my own turns in some situations, being able to counter a lot of what they do. BG3 makes you feel completely helpless during the enemy turn by omission of these mechanics in comparison.
Oh yeah, I should probably explain Legendary Actions for the uninitiated. It's a feature that certain very powerful enemies have in DnD where they can act independently of the turn order, 3 times per turn. They can also use one of their three charges per turn to instantly succeed at a saving throw as well. It's a concept not really utilized much even in tabletop unless there's a really good justification for a boss having that kind of thing.
I explain this because we should probably expect to see bosses with Legendary Actions in the later parts of BG3 as well. If the current combat design remains as is, that should be very scary to many of us.