Im unsure what is currently wrong with the current rules out of the complaints of AC class which from what i understand (in my limited knowledge of dnd) is that it effects accuracy to much?
I have to say for the health of the game, and not the table top, the current new rules are better, because it offers exploration and potential for new builds. This is highly important. If you wanted original rules you could just opt for other dnd accurate games. As far as i have seen the current bg3 is fairly perfect out side of a few things.
When it comes to accuracy, you can simply change the equations slightly to offer a slightly better accuracy rate. Having lower AC makes the game much more interesting in the way that it validates tanking oriented build more inline with current industry standards of using a holy trinity (heal, tank, damage) form of game play. This is highly important for validating specific fighter and cleric builds geared toward that feat. If it was easier to hit people these builds, and subsequently heavy/plate armor would be heavily invalidated.
As a senior game designer i can recommend for you to provide feedback, and if there is enough of an outcry it should get fixed, but I'd rather you just find ways to alter the current game mechanics to be more of a compromise with the current system so the dev team can focus on pumping out more content, classes, itemization and races.
Kind of a real question for you as a "senior game designer" that maybe will bring you closer to understanding what many people's problems are with all of Larian's homebrew rules.
If you spent literal decades tuning and refining your own personal game, to the point where you felt it was basically as balanced as you could have it, and some other developer decided to do a sequel to your game where they arbitrarily changed around large portions of the game's mechanics and added completely new ones as well because they found it to boring as is...you wouldn't have any problem with that?