The draw to you maybe. You're in no position to generalise about everyone else.
The main story to BG2 isn't that complex. Mad wizard abducts you, you escape, rescue Imoen, get back your soul, kill baddie. The story to one is even more bare. You go through 60% of the game before you hear the name Sarevok and 90% before you realise he's the same guy you met that killed Gorion. Nothing drives you as a player to follow the main story, except quest givers and it's a videogame, so why not?
What made them popular to my mind was they were first games that married (for then) decent graphics, with videogame concepts and the world of d%d and Faerun. Done with humour. And, when it came to BG2 great characters. And yes, romance. I remember reviews making a big deal of it back then.
Story wise Planescape Torment and Mask of the Betrayer are better arguably thematically with more player agency, a more complex central conceit. But BG is regarded as more of a classic. That's because BG did other things right too, especially 2. Great battles, puzzles, a great performance from David Warner, a few superb dungeons, interesting enemies.
Overall you have to look at BG as a whole, 2 1/2 games to judge its story. You're comparing this to one act of EA. The story of BG3 is the thing that's got me most excited.
Also, if you rate the romances in BG2, try out Anomen's. You're in for a shock.
I quite like the Shadowheart scene. You share a bottle of wine, looked at the stars and she may or may not confide a bit in you
A lot of people enjoy dnd because it let's you roleplay a character. Kinda sounds like you look down on these types of people.
The core story of BG1/BG2 is simple but delivered in a very solid narrative. The writing and voice acting were very solid and sometimes even stellar. But what really stood out was the political background and all the lore that was detailed for you throughout the world. It made feel you were in a living world. That was the charm of BG1/2 story.
I like the main ideas for BG3, but I feel the writing is off. The characters seem immature with some silly dialogues. I feel that Raphael and Astarion should be menacing but they sound comical.
A solid narrative does not a classic make. Apart from that the points you mention are more or less what I said. The attention to detail and the sense that this world was really alive is what sold BG.
As for characters, don't forget this series had Quayle, Tiax, Jan Jansen and even Khalid. Sure, a few of these were comic relief, but look at a fan favourite, Edwin. He's a lawful evil Red Wizard straight up murderer. Yet he's also bumbling, pompous and very very funny. Bioware weren't afraid to write characters different from 'how they're supposed to be'.
Astarion shouldn't sound menacing at all. He should be *charming*. He's never tasted human blood, feasted on nothing but rats and insects for 200 years. He's pretty pathetic at the start of the game. But he maybe should have the potential to be menacing, show a hint here or there. So should Gale to think of it. I personally really hate bringing Astarion along as a character, but I do recognise he appeals to the "I can save him" tumblr crowd. Which is okay in my book. Why shouldn't someone with different interests to mine also be catered for?
The devil should instil wariness more than fear. He's not a demon, violence isn't his m.o. Like Innateagle says I think the companions' reactions are right with most wary and Gale thinking he's clever enough to outsmart him. I hope it blows up in his face
I'm more a fan of the lore than the minutia of mechanics. I really don't care if they change a few things here and there. What excites me about this game is the lore and the possibilities. At it's heart it has Shar (possibly Selune too), Jeargal and the Dead Three, githyanki, mindflayers, the hells and devils, the Black Network, hints of the Shadow Thieves. This is the first game since BG that could only have been set in Faerun, rather than have that backdrop added like a coat of paint the way NWN 1 and 2 did. I'm pretty sure that of all the current companions Shadowheart is going to be the only one I take along on my first full playthrough of the main game.
I have a feeling also that WotC have learned from their mistakes and are going to integrate the lore of this game into campaign lore in a way they never did until recently.
