The game is a lot more enjoyable when you understand the 5e ruleset IMO but most people usually don't read tutorials (much less a 200 pages handbook xD)
My guess is most people would go and watch youtube guides if they want to learn the ''bg3 ruleset'' but I do agree the game should have all the information whether people read it or not (tutorials and codex)
I know there's a few tutorials already but I don't think they're nowhere near comprehensive enough to learn everything there's to learn. I might be wrong tho, it's been a while since I last played and I don't really have any use for bg3 tutorials.
I pray I DONT come accross as an elites some how.
I have played dnd in the past, Never 5th edition and I jumped in with no problem, Honestly I think people are WAY over thinking this. THe game isnt even really pnp (pen and paper dnd)
You read the dialoge you make choices, you hit things and kill them. If you have played any game in the last 40 years, from Atari to Sega to Nintendo to PlayStation, you should have no issue playing this game. Really, jump in and play, youll love it