Ok Mijati,
Rather than quote that entire wall of text again I'll try and address each point in turn.
If Larian did what you asked and used the 2nd Edition rules, those rules have been out of print for 22 years. Most D&D players today are younger than that and either grew up with 3.5 edition or picked up 5th edition in the last few years. Most BG-3 players, I suspect, come from previous Larian/Obsidian/Bioware titles and have limited knowledge of any D&D rules. So why would Larian implement a rules set over 2 decades obsolete?
Also, BG-3 is not a continuation of the Bhaalspawn storyline.
Baldur's Gate 1 & 2 were set in 1369-1374 DR. Baldur's Gate 3 is set over 100 years later. A lot has happened to the Realms, much of it bad*, and the Sword Coast has changed massively since then. For starters Eilistraree and Llolth fought a war for control of the drow. While Eilistraee ultimately failed, many drow had their Seldarine curse lifted and sought the surface. The Drow in general are now far less penalised by being on the surface.
Even if none of that had happened the Seldarine drow, led by Qilue Veladorn, have existed and been around since the beginning. Heck, Dambrath is a whole surface realm of the Utter East populated by a matriarchal tribe of half-drow called the Crinti.
[*both IG and IRL-- I'm looking at you, 2008 4th edition soft reboot fail.]
