It was very clear from available game footage and developer interviews that BG3 was never intended to be a tabletop emulator, or a tabletop game-aid; unlike NWN/NWN2 which were both designed to be used in that way. There have been no guarantees of providing anything beyond a story-driven co-op RPG; everything else that has been mentioned by Larian is aspiration, at best.
If anyone posting here thought there was a promise to implement 5e closely, then that is wishful thinking.
Larian have never said they cannot implement the 5e rules exactly; tabletop RPG rules sets are sometimes exhaustive, but rarely exceed simple arithmetic in mathematical complexity. What they have said is that the 5e rules do not always work well for the game they are making and the broad audience they are aiming to please.
Two points here: One can wonder why WotC went with Larian given the intention of not adapting the 5e rules, or why they did not enforce a faithful adaptation, which would be better for their product (the D&D books). IMO that's a bad strategy from Larian and WotC. D&D has an estimated 40 million playerbase, if they went with a faithful adaptation, they would be drawing from the D&D and CRPG public, and a fraction of this would make a smash hit. DOS playerbase is much smaller, so it seems strange to focus on those, given that probably a large share would buy the game regardless.