No offense to OP but maybe the game isent for you then?
Forcing misses (or at least migrating damage) is what heavy armor is all about. Characters can still tank at a pinch with dex but thats more the dodging and evading part of AC. You dont SEE that in bg3 which might be a valid complaint but missing or hitting is all part of the game. Negating that would just turn the game into 'who goes first, wins' simulator...
Why would I raise one of my characters AC by 2 with a spell if he gets auto hit automaticly?
Why would I wear a shield?
Why would a knight want to have armor if it offers no protection and even gives him penalties to beeing stealthy?
Why put points in DEX for non-ranged/or DEX hased fights at all? That AC isent going to be doing anything anymore.
I could go on but no, this game does not need an autohit feature.