I wouldn't say the writing is subpar, that would be unfair. I think the writing is convoluted due to the huge number of possible story permutations. Writing to encompass 8-10 characters with their own branching stories within the same active scenario is incredibly difficult to do without leaving great holes in the dialogue and story plots. It is made even worse when you try and give every companion unusual and complex personal backstories within said scenario. Nobody is "just some guy/gal" doing nothing particularly interesting before "event".
The writers have been given the job of writing a monumentally complex story which has the effect of making the story linear. It makes it linear because to branch 8-10 story arcs from the main plot would be an unrealistic number of variables. This is why the McGuffin (tadpole) is basically rime and reason you cannot do anything BUT continue down the same path. EA is basically a bunch of dead ends leading you to a single path with no variation. It makes it almost cliché storytelling but it isn't the fault of the writing.
If you "custom character" were written as the protagonist with maybe a couple of prologue backstories like DAO depending on class it would be easier to branch interesting arcs. When the companions only have to react to your decisions it is easier to widen decision making variables, reactions and relationships. When you add many protagonists all these protagonists have to react to each other as otherwise it make no sense.
