Probably because Revan is a hardcore fan.
And I guess the fear of all us hardcore fans is the fact that as the "world moved on", the writing and NPC interactions in games has become a bit worse and uninteresting... and I just don't get why "awesomic graphics" also mean "poor npc interaction"
Also, I assume Revan means that having a BG3 with another engine and with D&D 3.5 just wouldn't *feel* like BG, no matter how well created the story is...
Now, about BG1, it was extremely boring, granted, but it was a very pure RPG (NWN doesn't beat BG to that, sorry. It beats it to many other things but not roleplaying. I found NWN much more boring that BG1, and that's a lot to say ). If you are interested, anyway, there is a mod that adds NPC interaction. Lots of it!
Anyway, if you get BG3, make it nicer visually, use another engine, add lots of very well written NPC interaction and then call it "Dragon Age"...