Based on my own personal experiences playing BG2 I think I a lot of you guys are over-exaggerating. I played the game 5-6 years ago for the first time with pretty much no experience with any D&D system, and was able to complete the game with not much ULTRA METAGAMING EXPERIENCE like you guys go off on. Sure I struggled in some places, but I pretty much bumbled through most of the quests without being punished the game that much. Leveling and decking your characters out is pretty straight-forward so all that is left is gathering the right tools for the job. Even that doesn't vary so much other than equipping spells for certain enemies that scream "HEY THESE DUDES ARE EVIL, THIS WILL PROTECT YA!" and "HEY THAT CC SUCKS, USE THIS BUFF AND ITS OKAY". Vanilla AI Mage scripting is kinda weak, so even lacking the spells to deal with their protections you can even wait out them in a lot of cases.
I guess I come from a different generation where reading manuals/dying and reloading to win wasn't considered bad design. I loved playing action games like Ninja Gaiden/Devil May Cry where bosses would punish you terribly until you learned their move-sets. Its often why the "meta-game" knowledge complaint ends up ringing hollow to me. Its natural extension of just learning the game and its systems. Try too hard to mute specific threats and you run the risk of everything being solved by bland and brute force strategies.
I'm replaying the game right now for the 2nd time with the SCS mod installed(improved AI all around), and its only reinforcing my opinion. Its easy to struggle right away because you lack the equips and spells to deal with some threats, but once you start rolling you can end with most things handily. My assassin can chunk most mages in one shot, and I rarely need to change up my mages spell selections besides some cleric spells depending on what we're facing. With haste its easy to pop some emergency buffs on before you get slammed.
Even after successfully completing BG2 and its expansion the first time, its amazing to come back to the game and still have such depth to delve into. With the SCS mod I feel like I'm playing the game again for the first time and loving it. Most RPGs these days its way too easy to completely master the system many hours before completion(JRPGs are especially guilty of this), so it becomes a slog. Games like Dragon Age Inquisition are such an abomination that you can literally brute-force the game with simple strategies through the entire game on the hardest difficulty.
That isn't to say IE games are perfect, and a lot of the save or die and cheese spells needed their edge removed but modern RPGs are so muted that its simply boring. This might come down to encounter design, but the fact most fights can be solved by such similar strategies is lackluster.