Dodge should have been very simple to implement a long time ago.
My guess.. they don't want it in the game. A passive defensive feature goes against some Larian philosophy where every time a player presses a button something spectacular has to happen. (And even if it's mundane like just running, it needs to look spectacular anyway.)
Tactically, Dodge wouldn't be very useful in holding a defensive position or hallway anyway. Because you can't hold any position in BG3. There are no positions. If there is no space, pigs and minotaurs just fly over you, and goblins start spamming AoE fire bombs. Or you just get Bonus Shoved or Thunder arrowed 30 ft. away from your position.
I think this whole thing runs deeper than just implementing a Dodge Action. There should be a clear shift in BG3 development to move away from the meme style combat where you hilariously slap people into lava and blow them up with barrels you find on the road, and go for more tactically sound D&D combat instead where actions like Dodge matter.
Ready action would be useful if line of sight and cover played a bigger part. And if you could hold defensive positions to protect your weaker party members, again.
