But IMHO D&D 5e have some mechanics that are simply not manageable in RT nor RTwP (reactions, help, delay, bonus actions, etc, etc, just find lots of examples in this thread) Even game developers like the ones of Solasta addressed that. And any player with a minimum knowledge of the tabletop knows about it. But I do not think Larian is going for a perfect adaptation, and even Miles Myers of WotC accepted that; they are open to change things.
I agree that 5e gameplay working in a smooth way might be difficult to implement. Having reactions go of asking if you wish to activate this and that will probobly be awful. Reducing perfect control for players by implementing automated triggers might be a way to solve it. For counterspell they could let players decide "use this if enemy casts 3;rd level or higher spell or a healing spell." as an example. I dont see any problem with bonus actions / free actions etc.
Ok, it was already discussed so I keep it short: I do not think it is impossible but I think it is not manageable. First of all, one turn is usually 6 seconds. You have one action or ready action, one reaction, one bonus action per character and per turn. And I think you will have 4-5 characters in your control. that makes 5x3=15 actions in 6 seconds plus the enemies actions. You have to automate a lot if you want to make it manageable. And BG will be a MP game. If you make reactions automatic they are not reactions anymore. I mean, It is ok if you make attacks of oportunity or counterspell automatic, they already made it in NWN, P:k, etc. But you only have one reaction per turn, and if they do not allow you to choose if you want to use it or not, or against whom you want to use it (maybe you want to block with your fighter or use cutting words with your bard against the bashing of the ogre, not against the goblin with the dagger. Maybe you want to protect your squishy caster instead of your full-armored fighter; or even do nothing at all. You cannot do it if the game makes automatic choices for you). Also, not all reactions are easy as counterspells or attacks of oportunity. In RTwP you do not know the initiative order, so the tactical options of ready, delay or help do not make sense or are not even useful because of the turns last 6 seconds, even if they allow you to use them. You simply have the next action of the next turn to worry for, why care?.
Normally there are no problems with bonus actions like attack with the blade in your left hand because you do not have to decide anything in there, but In pathfinder and some other games, in my experience even if you use your bonus action to, for example, mark an enemy with your hunter or cast a quick spell you usually have to wait and make another pause in less than 6 seconds to do another action, because if not you lose the action in this turn(because you make a simple attack instead of using a skill, move, cast another spell, etc) and you have to wait to the next one. Make it five times, one for each character. At least some core features like advantage/disadvantage or inspiration could be easily translated to either TB or RTwP. And before you say anything, it will be a MP game, so forget about using "pause after cast a spell" or things like that because you are hampering the progress of the other members of the party. Let´s be realistic here. If you ever played BG2 in MP you know what I mean.
I know many people do not like to micromanage or do not care about most of these tactical features or some others, but there are people like me that do like them. I a game RTwP game, even more, MP RTwP, I am afraid that most of this fun features are going to be automatized, cut off or simply you nor the enemies are not going to use them due to time restraints.
I do not mean to say that BG3 must be a perfect representation of the tabletop game, because I already have the tabletop game to do that, even if that would be awesome. As I said before, I am ok with pathfinder or 2e, 3.5e videogames in RTwP, but IMHO do not think 5e is suited for TB because several tactical options and fun features are going to be watered down, and the devs of Solasta agreed with that vision, and they know better because they are already making a videogame out of it.