That either means the writers aren't doing a good job, they don't have time to do a good job or they don't care.
Personally I don't see what you are trying to say. The story in DA2 is not dependent on the save import in the first place, so where is the connection? The only bits that are directly involved in the plot is Anders and Leliana being alive.
I don't see the limits of the Save Import directly tied only to the information imported over that was directly retconned. In fact, retcons don't bother me in the least.
It is the concept that previous stories cannot be referenced in large ways. This goes beyond what David talks about in the quote I used above (or the statement he made earlier today in a different canon thread) where players may have the expectation that every choice they made will result in their own personal world being created. The fact that the games don't allow that is not the problem I perceive.
The problem is, instead, the fact that previous stories cannot be continued on with the Save Import. Ironic, I know, but it is true. Because a number of people could be on the throne of Ferelden, it will never matter who is on the throne. That is to say, it will not be different enough to tell a different story. Allistair on the throne means the same for the country as Anora or the Warden or any combination of the three.
Instead of one choice being taken as canon and advancing the story of Ferelden, ALL choices are carried forward, meaning the world is roughly the exact same, regardless who is on the throne. Could a writer tell a really amazing story about Allistair being on the throne and supporting the Mages while Anora, locked in the tower of Fort Drakon, secretly plots to overthrow him by throwing her support with the Templars? Sure, it sounds like an intriguing enough plot. But the writers CAN'T tell that story. Because it depends on certain choices in DA:O to match up and any one given story can't deviate too much from the beaten path of the others.
I could give similar examples about the king of Orzammar, or the Urn of Ashes, or the rate of Feynriel, or the life of Anders... but they all paint a similar picture. The Save Import makes all choices given to the player inherently diminished in the scope of what can happen because of them and work to limit what the writers can do with any given plot. Once the player has touched it with a choice, the story becomes reduced to a situation of straddling a middle ground that either halts the development of that storyline completely or results in a retcon.
I don't have a problem with the retcons or playing in a world with different choices than the ones I picked, because I understand that it makes for a more compelling game when the writers choose what stories they want to tell, including how those stories are set up initially.