For mine the thread of development that has created the most harm:
(Ultima 6-7 companions lead to) Baldur's Gate 1 popularised the concept of recruiting walking talking bickering "companions" for nerds like us that didn't have that in real life. This led to a natural progression of Baldur's Gate 2 Romances which was the floodgates for decline; it was these romances that first attracted non-rpgamers who in turn brought all of these demands about what the genre should be.
(Ultima 6-7 companions lead to) Baldur's Gate 1 popularised the concept of recruiting walking talking bickering "companions" for nerds like us that didn't have that in real life. This led to a natural progression of Baldur's Gate 2 Romances which was the floodgates for decline; it was these romances that first attracted non-rpgamers who in turn brought all of these demands about what the genre should be.