However, I think we also need to contextualize the kind of game ME2 is: It is a pure character study. The entirety of the major missions in ME2 are all either recruitment missions or loyalty missions. The entire game is centered around exploring the personalities of the characters. That's why characters like Grunt, Mordin, Jack, and Thane feel so remarkably fleshed out and deep. If 100% of the content in BG3 were character study of our six origin companions, we might be having a different conversation.
I wonder though, is BG3 NOT a character driven RPG as well? When people talk about why they love the game, the characters are almost always at the forefront of the discussion. The recent rush to defend poor Lae'zel, the constant SH fanart, the Halsin memes, it's pretty much all people talk about. The actual main plot? The villains with an exception for Raphael? All very 'eh', very similar to ME2's main driving plot. The plot is a backdrop for character interaction/development.
Also, each Mass Effect game is 30 hours give or take 5 hours or so. BG3 if you're playing without redoing a bunch of stuff and steadily making progress, weighs in at about 100 hours, give or take 10 hours or so. You'd think BG3 characters could do so much more with their development in 100+ hours than a single ME game does in one (or even 2, because all it took for those characters to become legends were two games). Wyll? He's got a very simple story, with very few meaningful choices. SH? She has exactly ONE big moment, and then she's sort of just there. Karlach I would argue is the most developed. She has a lot of incidental interactions without the player character, main story tie-ins, a constant 'dealing with her issue' progression throughout the game, and a resolution (whether or not you like it) to her issue at the very end of the game. The rest though, I just don't see it.
Sure, I could reload and choose different dialogue options and get different responses, but that doesn't change their entire relationship with Tav or each other.
All this is obviously imo, and off the top of my head, so I might be not remembering things, etc. Grain of salt and all of that. That said, I need to play through the ME trilogy again, see how it holds up now that I've played BG3.