Old news no doubt, but aside from the retcons and the fact that the writers were afraid of anyone taking the campaign seriously, I've pretty much found the major reason why I consider the SC2 story to be a disappointment.
Do you guys remember the hype for SC2 before it was announced. Back then I wondered how they would script Kerrigan's interactions with everyone else, or what she would even do. At that point, the end of Brood War, Kerrigan has become the Queen bitch of the universe. She has pissed everyone off, and people would be stupid to trust her a second time. It got to the point where Kerrigan had to die as far as every other character was concerned. What kind of writing magic would the writers have to pull to create a plot where she interacts with others in any meaningful capacity beyond killing them all? How would Raynor live up to his promise to kill Kerrigan? How would Zeratul avenge his Matriarch? This was basically the hype for SC2.
Of course back then there were no prophecies or deux ex machina de-infestation artifacts in the SC universe, so I was counting on them using clever plot & character development to make this happen. Imagine my disappointment when they took the easy way out and created a prophecy which mandates that kerrigan must live or the universe will explode. What the f*** writers? This is the best you could think of?