Is there an answer that can satisfy, Tricky? By "everyone agrees" the creative genius is gone it sounds to me like you've already got a firm idea of what kind of games BioWare produces now, and that they're not your cup of tea.
Yes, the map is linear. It follows the same template as Knights of the Old Republic and Mass Effect: you get three or four missions, you decide what order you do them in, and after those the story kicks in and holds your hand for the rest of the game.
Yes, some sidequests are very MMO. "Get me fifteen of those." "Go there and kill these." "Go to all these locations and gather the pieces."
The first time I played the game I was disappointed with the ending because it seemed the developers dropped the ball on the fact that my romantic interest, a major character centric to the plot, was dead - and none of the NPCs seemed to care. In five years of development nobody thought to tailor to that possible outcome?
I don't know what the standards are for "substantial" conversations and characters... Baldur's Gate 1 had dialogs and characters that were certainly insubstantial, and the saga that stemmed from that game seems to be the so-called paradigm that every BioWare title since has been compared to. Just because a game has hours of voiced dialog doesn't mean it's substantial (See: Oblivion).
Personally, I find the game quite enjoyable. Bloodstalker and I chat about various characters, what we like about them, what we don't. Things that we like, and other things that are lacking. That said, I also really liked Mass Effect - and a lot of people did not. If you really have doubts I would suggest you try Fable's thread titled "First Impressions" where a lot of people gave their opinions on the game. That should be a more viable place to find the answers you are looking for.