Yeah, I have the same issues on one hand, that the encounters are too hard for the average user, but I can see that they can also be trivial once you found a way to exploit the system, or when you are very knowledgeable of the source material.
The real issue is that BG3 requires you to know an awful lot to succeed, but does not actively give you the knowledge and does not show you examples on how to make the best out of your resources.
For example, while I appreciate the hit-chances being displayed, I have no idea how it is calculated or how I can modify it. Now I can only guess that range and height, might have something to do with it and that it does not help to have multiple enemies around me, when I am trying to shoot my bow. I just came here to find how this is calculated and modified, the game never told me (or might have in two sentences with a tooltip), but it never showed me. It did not tell me that immovable, stunned or knocked over characters modify that (it is logical, but can not be seen as a given). Even the position of myself is important, which is horrible since it applies to me as well. So I am getting hit more, because my back was turned towards the enemy, and the game never told me how to rotate characters after actions/movement. If possible at all.
It is the same with sneaking. When I enter sneak mode, I never know what breaks it, or if my attack is a sneak attack. I assume that it has to do with the red area on the ground, which breaks stealth, but noone told me. Noone told me how to exploit or even apply sneaking in combat, so I just auto-attack with my sneaked rogue and maybe I am getting a sneak attack?
Also, synergy of skills and spells etc.. In the whole tutorial I never knew that when I locked an enemy with my crippling arrow that he will be knocked down with the ice bolt. Blood will also turn to ice. A sleeping enemy is prone to sneak attacks, probably a held person, too. I just today thought that I might be able to light my arrow on the candle that I just lit, I do not know though, nobody told or showed me. I am also not fully aware of how initiative works and how the enemies move and turn or what they are capable of. Is it good to go for the strongest first, or the caster? Or should I remove certain characters from the combat now, to deal with them later? If I want to use synergy, how do I exploit the turn times so that my character 1 who sets the trap comes before character 2 that exploits the trap?
Resource management and consumables: I have not yet rested, but most skills and spells naturally are not available to me now. I do not know what short and long rests will do, or if there are any penalties. I got the typical fear of using my bombs and poisons, because I do not know if I need them later in a harder fight. Nobody told me that in a game where you have one action and one bonus action and can move whenever and how often you want, you will face off against more enemies than you have companions, so reducing the amount of actions, bonuses and movement is key. A melee fighter that can not move also can not act. A ranged unit that lost his action can not attack, just flee. A silenced mage can only resort to low damage melee or ranged. And so forth. If haste gives me one extra action, it can mean that I can exploit my trap myself, so say I can throw an oil bomb, light my arrow and set them all on fire. Or I can fully take out a large opponent by myself. Or cripple two enemies negating their turns.
Environmental assets: So I can use the environment to my advantage? So this crane weight can fall down and take care of two guys? Awesome, however it only highlighted after I moused over it randomly, after the fight. This is generally a problem that not all objects you can interact with are highlighted, just containers.
Group movement: So I know combat is ahead, but my comrades keep following me when I try to setup a good position. I can not block a certain position with my melee fighters, because my mage trails in behind totally not in cover. I can only clunkily remove one, or select sneak individually to move them one by one. This system is cumbersome, unintuitive and hurtful in combat. You can also initiate combat by yourself beforehand and to setup, but this is also just explained as a sidenote and not shown as a tactical tool.
A perfect example of everything is a fight in the ruins that starts as soon as you unlock a door. So my main is a rogue, he opens the gate. My melee fighters are behind him and behind them is my mage. The enemies are mostly ranged. My rogue starts, unsneaked so I figure, best get a shot off and let them come to me. It only occured to me tonight before sleep that I could have lighted the candles left and right of the door, lighted my arrow and hit the oil barrel in the middle of the room, the stuff just never lighted up and I was never told. Next in line are three ranged dudes of them, they approach get in range to hit my mage and let loose, that is three arrows hit and the mage goes down. So reload and try to get my group into position, but I can not really, because of the movement system. So I do the best I can, start the fight in sneak, and manage to kill one guy right away. My plan is to cast a fog so I can move up my melee fighters, however initiative makes it so that I should have done that last turn, so my fighters can move up this turn, so it is delayed. Meanwhile one enemy just throws an oil barrel into the doorway and all bets are off again and the plan fails, as anyone moving through fire or acid will take a lot of damage. So I sit there until the fire is out and otherwise can only pop out and shoot arrows. Once it is out, I move, but the ash is hindering my movement, never knew that, so my fighters take a beating while not approaching as far as possible. My mage misses his fire bolt and the sleeping enemy is out of my shortbow range. The fight was not particularly hard, but it was long and not particularly fun, because my options were limited and I limited myself, because the endless possibilities were not known to me.
So all in all the combat is pretty unintuitive, cumbersome, unpredictable, hard and unbalanced because the possibilities are obscured and nothing is known to the player, since it is not taught or shown.