In an early interview, Sven stated that Larian's first build for BG 3 adhered closely to the rules of 5e, but they scraped it because Larian didn't find it very 'fun'. Specifically he referenced how often low level characters seemed to miss their target with their attacks.
Even a quick glance at this forum shows how much people want a BG 3 that adheres to the rules of 5e.
I would suspect that depending on the definition of "adhering to the rules" and "fun" there would inherently be a bazillion answers.
For all the complaints that combat "takes too long" well take that, multiply it by how often low level characters actually miss and you would not have a playable game for a large chunk of the current player base.
For all those that say "make it harder, I'm game" it's been a thing in past Larian games to have difficulty options, so there is that.
