I have played both of the Baldur's Gate games and they are probably my all time favorite combat CRPG, after throwing in things like SCS to turn up the difficulty. With that being said, what I enjoyed about it was the depth of mage combat, with contingencies. sequencers, etc. Things which as far as I am aware of, are likely to not even feature in this game and even if the game did go to 20, are substantially less interesting in 5th edition. Baldur's Gate also took some liberties with the rules at the time, so its not like BG 3 is alone in that regard. Ultimately, the rules of D&D are made for a tabletop game, they are not made for a computer game which means that when you adapt them, some liberties will have to be taken.
Yes, you could just implement cantrips for example 1:1 and completely gut surfaces as a mechanic, but ultimately, in my opinion if you were to implement the 5e rules exactly as is, they would make for a very shallow computer game. This is because whilst at a table you do not want to bog down a game with minutiae, when a computer is doing all the calculations, there is no "bogging down" and this allows you to have a much more complicated ruleset while still maintaining the same combat flow. TBH, 3e or 3.5e would probably make a much better computer game than 5e, but there was no way WOTC would ever allow Larian to use an earlier edition.
For me tactical combat is ultimately my main draw to these games. I personally approve of adding almost anything to the system provided it makes the combat deeper, but that is just me.
