I gave up trying to see who is doing what. ... it is really frustrating and makes me just tab out and do something else until my turn because it doesn't matter what is happening.
See, that's really not good player feedback in response to one of the core mechanics of a game - in this case, combat.
leaves them with combat that can often feel slow and heavy, but Also like it's not showing half the things it's meant to, or like it's struggling to keep up with what's happening
This. 100%. Some elements feel "heavy" while others feel like they're struggling to give the player a good sense of the action. It all needs a more measured pace.
Take a look at any modern turn-based combat game to get an idea of what is needed: XCOM 1 & 2, Wildermyth, both Pathfinder games (after the patch to Kingmaker), Gloomhaven, I could go on. There are plenty of examples of what good turn-based combat should *feel* like. I don't think BG3 is there. It has the bones for it, but it's not there.
